Thoughts on WG4 The Forgotten Temple of Tharizdun & The Cults of Tharizdun For A Modern Day OSR Campaign.

  It has many names The Dark God, The Ender, He of Eternal Darkness, the Ebon God, the Black Sun, the Patient One, He Who Waits, the Anathema, the Father of Elder Evils, the elder elemental god, the Author of Wickedness, the Eater of Worlds, the Despised, the Undoer, the Chained God, the Chained Oblivion & it has made the crossing. Since dealing with both my Castles & Crusades Wilderlands of High Fantasy & Victorious rpg campaigns. Veterans of the Supernatural Wars rpg has generated a ton of interest among my players. So an old campaign notebook entry reared its head. Could the cult of Tharizdun present a dangerous and viable threat within a modern day Earth?! "WG4 The Forgotten Temple of Tharizdun was written by Gary Gygax and published by TSR in 1982 as a thirty-two page booklet with two outer folders; there are no modules with the codes WG1-WG3. ", this is the publication history that we all know. 

We know that the release of Iggwilv & her daughter is going to create two cults at least upon the world both demon worshippers & a vampire cult. But the greater evil maybe lurking in the background of the campaign yet to rear its head & that's Tharizdun. 

Iggwilv is one of the keys to this & to this end I've placed an alternative version of her temple from S4 The Lost Caverns of Tsojcanth within  Maple White Land. Her black witch covens would have spread across South America, the lower half of the United States, & even up into the New England States. Why?! Her description gives her ambitions as not being seditary at all; "Iggwilv is said to have two forms, one of which is that of an old crone (said to be her true form), and the other, a human female of dark beauty. In the latter form, Iggwilv has long black hair and pale skin. It is said none who have seen her in her true form still live.^[16]

She has many alternate names. On Oerth she has been called the Witch Queen of Perrenland and the Mother of Witches. She is known as Louhi on one alternate Prime Material Plane world, and as Ychbilch on another. Those close to her sometimes address her as Wilva." 

The real goal would be to suck Earth dry & then move on while releasing  Tharizdun. What would slow both Iggwilv & her daughter would be the fact that they don't share power easily with one another. Gary Gygax's version of Grayhawk had Gord The Rogue travelling the planes as a champion of Balance after a new cat lord was inserted into his place; ""Evening Odds" appears as story 14 in Pawn of Chaos: Tales of the Eternal Champion, an anthology of fiction inspired by Michael Moorcock's Eternal Champion mythos. The story takes place some time after the events of Dance of Demons. Gord has apparently been deposed from his position as the new Catlord and is traveling the alternate realities as a Champion of Balance. In the course of the story he upsets a plot by the archfiend Baphomet on modern Earth." 

This places Gary Gygax's Greyhawk near to the Prime Material plane.  In fact that it also places The Wildlands of High Fantay near the planes Prime as well.
 Several magazine articles in Peagus magazine the Judges Guild house magazine have the Wilderlands cross over near Earth's sphere. This very idea makes Earth a prime hunting ground for a number of Dungeons & Dragons monsters. 

Tharizdun might already be touching a piece of the Earth's plane within this campaign world version of  WG4 The Forgotten Temple of Tharizdun. The cult of Tharizdun would rely on its inner circle members to be nilistic & dangerous undead fantics. Fanatics who would do anything to further their various masters agendas. There are plenty of idiots who would fall for the false promise of immortality that undeath brings. So the ranks of these cults would swell like a disease sweeping across the world. We've seen this type of event time & again within our modern world. Right now its just spit balling ideas out here: 

1. A party of adventurers is brought together from  across the planes & Earth by the powers of the Balance to stop the destruction from happening. 
2. These cults go to war against one another because of each one wanting to seize power.
3. Those who make a cross over unto Earth risk being stuck here for the rest of their lives.
4. The powers that be use Earth as testing ground for young adventurers. 
5. The hidden & lost places of Earth allow one to cross over into Greyhawk & the Wilderlands. 
6. The minor gods of the Wilderlands can have influence on their agents on Earth. 
7. The occult & the supernatural are a cancer on the planes allowing Chaos & Law to gain foot holds that cause the planes to go out of balance. Thus bringing in exterterminators to hand the problems. 
8. The Gord The Rogue novels show a clear campagin path to bring in classic D&D elements into a campaign setting. 
9. Greyhawk has some excellent campaign points to exploit for the player's PCs & they won't be expecting it. 
10. Standard D&D magic may be much more dangerous on Earth. 

Earth & Alien Sky - Carcosa & Elf Lair Games Veterans of the Supernatural Wars Rpg By Jason Vey & Tomothy Brannan Session Report & Monster Workshop

"We Are the Night Shift...
We alone stand against the vampires, werewolves, and Things that Go Bump in the Night.
We know the things that prowl the shadows, the monsters that feed on the innocent.
We have seen Something Weird.
We control Something Weird
We create Something Weird.
We study Something Weird.
We are the things that Weird Things fear.
We are the Weird.
We are the Night Shift, and we are all that stands between you and the end of all that you know."

What happens when invasive aliens won't stay in their own damn lane of reality?! We're talking about the B/X system Veterans of the Supernatural War & specifically the idea here that Lovecraftian gates are opening across the Earth. The faithful are assaulting the Earth with energy weapons, guns of advanced design & even flying saucers. These invaders wield powers beyond human ken and only you can stand in their way! 

Let's talk about Carcosa for a moment shall we? We've spoken about how Carcosa is a horrid & dangerous place. But why is Carcosa a horrid & dangerous place to Earth?! Geoffrey McKinney's Carcosa has always had a reputation but when gateways open & weirdly colour humanoid tribes pour across the Earth only the Nightshift can stand against them. So the campaign might be a combination of  Hammer horror, cosmic terror, & absolute Jack Kirby terror combined in one mini campaign idea. Carcosa is a nasty business all around. The spells are nasty, the sorcerers are mostly evil, & even the technology has a bad reputation. 

So the stars turn right & now the gates to Carcosa open right around smallest towns strange mists begin to form. In these same towns many feel the call of the saints & old gods, the Divine Warrior answers the call. Entire cities are emptied as strange alien mists retreat back into their planar windows. Cities have entire neighorhoods in major cities are emptied out of people and on Carcosa the blood flows as alien gods except their due. 

Across the Earth magicians, witches, & covens gather to discuss the situation as packs of werewolves howl at the blood moons that rise across the world. Vampires from acros the globe prepare their armies & hordes. The first battles happen as air ports become choked in mists & the evils of long dead & forgotten civilizations rise out of the Earth. Even as blue & green skinned humanoids blast away Earthmen with weapons of alien design.
This mini campaign would depend on  NIGHT SHIFT The Night Companion kickstarter  which is nearing its last few days. Why?! Because of the fact that there's so much more potential with the expanded PC classes. 
Carcosa itself is absolutely a nightmare & add in the Lovecraftian elements & it becomes a major OSR campaign shift point in my opinion. 

The Path of Forever - The Profane & The Hellish - Elf Lair Games Veterans of the Supernatural Wars Rpg By Jason Vey & Tomothy Brannan Session Report & Monster Workshop Now With More Kasimir Urbanski's "The Invisible College" rpg

"I embrace hardship and privation with ecstatic delight; I want everything the world holds; I would go to prison or to the scaffold for the sake of the experience. I have never grown out of the infantile belief that the universe was made for me to suck. I grow delirious to contemplate the delicious horrors that are certain to happen to me. This is the keynote of my life, the untrammeled delight in every possibility of existence, potential or actual."
Ch. 54
The Confessions of Aleister Crowley (1929)

This blog entry picks up right where our last blog excusion left off. We go  into the bowels of a supernatural & occult  thought exercise in a campaign set into a world of  mixing  both 'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan & Kasimir Urbanski's   "The Invisible College" rpg  at the table top. 

So what scares some members of Kasimir Urbanski's   "The Invisible College" rpg? The samething that has scared members of every occult & supernatural society from time immorrial. And that is death. Even those whose practices can create bolts of supernatural damnation must & will bow to the blade of the reaper as will we all! Or will we?! In the highest levels of occult sciences & supernatural practices there are literal physical immortals who practice immortality at a very high end of the scale in  "The Invisible College" rpg. 
So there are literally immortals who might have been around since the forgotten times of mankind. Immortals who are quite literally willing to do anything to secure their own fleeting immortality. Sacrifice an enite people or country?! No problem at all. Genocide an entire civilization? Sure why not to ensure another two thousand years or so. These monsters of the  "The Invisible College" rpg are the true manipulators who move entire family lines of minions just get their points made. These immortals are invited onto the path of divinity & then things get weird. Even these monsters pale in comparison to the true manipulators of evil & good. We're speaking here of the B/X immortals those who have the insane desire to walk the next path of immortality. 

While it is possible to step from the "The Invisible College" rpg to the Frank Mentzer path of immortality. Its going to be very rate indeed. Because the incredible price that must be paid is very high in both occult power & ingrediants to maintain  existence. These immortals sometimes create for themselves cults around them going against many of the principles of magick itself. According to Crowley, " I do not want to father a flock, to be the fetish of fools and fanatics, or the founder of a faith whose followers are content to echo my opinions. I want each man to cut his own way through the jungle." Some of the immortals merely want ot maintain their own grasp on phyical & spiritual power. They use their own  wizards as immortals use other adventurers to fufill an agendas of temporal & mercurial power. 

Both sets of immortals often bring themselves into conflicts with mortals & magicians who are far down on the ladder of adventure. This pecking order is the same that we see time & again used in fantasy author's creations such as Michael Moorcock's dark fantasy & science fiction creations. A pecking order well established within   Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan.

Not only are wizards of the "The Invisible College" rpg aware of other worlds such as Greyhawk or Mystara but they absolutely seek these out for the rare ingrediants that such places hold. The cross point is that risk of the immortals or gods of these realms becoming aware of the supernatural tresspassers into their realms! A fact not lost on the demonic & infernal hellspawn of Rafael Chandler 's Demonic Tome 'a pay what you want title' . 

But why?! What draws the infernal to these magus of the "The Invisible College" rpg as more then simply another meal or soul?! We'll get into that coming up because nothing lasts forever. Not even immortality itself. 

Picking Your Battle Grounds - The Profane & The Hellish - Elf Lair Games Veterans of the Supernatural Wars Rpg By Jason Vey & Tomothy Brannan Session Report & Monster Workshop Now With More Kasimir Urbanski's "The Invisible College" rpg

" Do not imagine that art or anything else is other than high magic! - is a system of holy hieroglyph. The artist, the initiate, thus frames his mysteries. The rest of the world scoff, or seek to understand, or pretend to understand; some few obtain the truth."

Aleister Crowley


The problem as its been seen by fellow DM's is the fact that we're so eager to believe in world grinding conspiracies these days. Corporations engage in campaigns against their own consumers. Governments hold on to power anyway they can & where does this leave the common man?! With mystery & magick! If you think that our reality is the only one. Think again! This blog post picks right up from our last one here. 

You've got to realize that travelers between planes & dimensions are not going to tell anyone who they are in reality. They get along with their occult assignments & move on. The world's inhabitants are going to turn to the 'subtle sciences' of magick & the occult. Last time we asked the question 
 is there room enough on the table top for both 'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan & Kasimir Urbanski's   "The Invisible College" rpg  at the table top?!  And the answer was yes! 

If your expecting gouts of Hellfire & brimstone those are isolated incidents straight from horror movies & they happen.. And Hell isn't interested in taking apart the status qou. If anything Hell is interested in maintaining our reality as we know it.



This is right in line with the precepts of the definition of Lawful Evil. By its very definition it comes darkly into play; "

Lawful evil is sometimes called "diabolical," because devils are the epitome of lawful evil. Lawful evil creatures consider their alignment to be the best because it combines honor with a dedicated self-interest. Lawful evil is the most dangerous alignment because it represents methodical, intentional, and frequently successful evil." So the traditional definiation of fist edition Advanced Dungeons & Dragon's alignment stands at least until the trumps blow for Revelation. Let's go straight back into the fact that the things you actually have to watch out for on a street level game are going to be the demons. These things of the Abyss straight out of the D&D Rules cyclopedia are going to be more then a match for the average magus even in the Invisible College  rpg. 

The Abyss operates exactly as Crowley talked about black magick, "Black magic is not a myth. It is a totally unscientific and emotional form of magic, but it does get results — of an extremely temporary nature. " This is the very essence of chaotic evil & Chaos itself. Temporary results or the quick way of power. The convient way of power is the quick path of that power. When power is offered on a plate in unexpected ways humans jump at the chance. They seldom realize where this power originates. So where does using Rafael Chandler 's Demonic Tome 'a pay what you want title'  come into play? It comes into play as these demonic forces begin to invade the PC's life. They bleed into reality from backrooms, the board rooms, & from your neighbors.  The infernal & Abyssial  universe right next door is knocking. And it wants in. 

The only ones who can stop this are going to be those movers & shakers of the Kasimir Urbanski's   "The Invisible College" rpg. These magus can & will change the results of a battle field in Eastern Europe, the skyrocketing economy of a first world nation, & cut off the supply of success to Silcon Valley firm. International corporations &  governments have been using these demons & evils as subtle  weapons for decades.  And this weakening of the fabric of reality has been allowing other planes to wash up against our reality all of the time. People can wander into other times & places only to come back changed. This is the origin for some of the PC's in our own campaign version of Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan.

These wash overs of other realities happen at the fringes of our own. These create the ruins, dungeons, etc. that PC's are called to. These are places of the otherworldly & places created by the otherworld forces that over arch our plane from elsewhere. If this campaign of thought seems influenced by Michael Moorcock it rightfully is. We'll get into that next time. 

The Profane & The Hellish - Elf Lair Games Veterans of the Supernatural Wars Rpg By Jason Vey & Tomothy Brannan Session Report & Monster Workshop Now With More Kasimir Urbanski's "The Invisible College" rpg

" If you examine the highest poetry in the light of common sense, you can only say that it is rubbish; and in actual fact you cannot so examine it at all, because there is something in poetry which is not in the words themselves, which is not in the images suggested by the words 'O windy star blown sideways up the sky!' True poetry is itself a magic spell which is a key to the ineffable."

Aleister Crowley

This post is gonna pick right back up where this blog post ended. Today we're gonna rewind the clock back a bit. Because we got together last night & began to discuss B/X OSR rpg options & resources. 
Why?! Because we hadn't examined one or two B/X occult mega resources for 'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan. Namely Kasimir Urbanski's   "The Invisible College" rpg from Amazon. You can read my review of 'The Invisible Colllege' here. 

Right off the bat this blog post is made with the following warning. I don't care about any of the rpg designer's political views or camps. Timothy Brannan over the years on his 'Otherside  blog' has reviewed lots & lots of  Kasimir Urbanski's rpg titles & vice versa. So let's dive right back in. 

"Indubitably, magic is one of the subtlest and most difficult of the sciences and arts. There is more opportunity for errors of comprehension, judgment and practice than in any other branch of physics."

Aleister Crowley

 So lets get back to the fact that 'the Invisible College's occult & mundane forces  may be the only thing standing between our normal reality & infernal Hell on Earth. I'm not talking Harry Potter here but the promise of the Golden Dawn realized! The idea that visitors from one universe might be coming to pollute our own during the Eighties! The Sixties occult awakening led to the Seventies Supernatural Cold War. But both Russia & America realized that each other wasn't the true enemy here. The powers that be of the Invisible College are minor players in the B/X multiverse here. 

The Invisible Collège offers full on B/X style occult demons. So let's go with that for a moment. These are scouts straight out of the multiverse probing for weakness within the fabric of our lower vibrational quantum reality. International governments have been using these demons & evils as subtle  weapons for decades. 
World of Darkness?! Cthulhu?! No this is far more dangerous stuff here. These demonic forces from the Plane Prime next door are weapons of mass deception of the highest caliber. 
But is there room enough on the table top for both 'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan & Kasimir Urbanski's   "The Invisible College" rpg  at the table top?! 
Yes & in point of fact here's my suggestion for the cults that are trying to bring about the destruction of the Earth! Grab a copy of Kevin Crawford's  Silent Legions rpg in addition! 

Why?! Because the real enemy who'd be trying to wreck the world as we know it would be the supernatural  cells & cults springing up in board rooms & back alleyways across planet Earth in the Eighties. 

Think about it?! Your neighbors, your friends, relatives, & strangers might all be veying for power across your home town. The real issue? What if they get it? What if that power comes from a whole other universe whose supernatural cancer wants to spread?! Would the cure already be in place?! That's where 'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan comes in. With these three powerhouse games you as the DM can build ANY supernaturally oriented campaign from the ground up! This will have years of miliage within it! Why?! Because essentially this is all OSR B/X powered supernatural & occult goodness. You can & add or subtract as needed. 



Where does using Rafael Chandler 's Demonic Tome 'a pay what you want title'  as the basis for a Horror Pulp style invasion of Hell on Earth come into play?! Soon but let's take this slowly because we're in the middle of Hell folks! 

The Profane & The Hellish - Elf Lair Games Veterans of the Supernatural Wars Rpg By Jason Vey & Tomothy Brannan Session Report & Monster Workshop

 "Demons feed on innocent souls and obliterate cities. Human victims are possessed, devoured, and damned. Unfortunately, the world's last line of defense is a group of ultra-violent cannibals wielding unholy magic."

This is a follow up to yesterday's blog post on retooling our Veterans of the Supernatural Wars rpg. Today we started discussing 

'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan could have an infernal campaign definited by a band of infernal NPC demonic villains & we've got the perfect OSR  solution. 



Game campaigns are often as good as the enemies that the players are facing & sometimes its all within the enemies. Welcome to the Eighties when the Earth went to Hell & the demonic came home to roast! Now what happens  when the 'Heroes of New England' have the demonic neighbors from across the dimensional dive come to call?! The 'heroes' from one universe could be the demonic evils of another universe! What the Hell are you talking about?! We're talking about using Rafael Chandler 's Demonic Tome 'a pay what you want title'  as the basis for a Horror Pulp style invasion of Hell on Earth. 

How do you describe this one hundred & thirty two page OSR supplement/modernish campaign setting!? Well try & imagine the Bible's Book of Revelation combined with White Wolf's Hunter The Reckoning but with an OSR death metal paint job this is 'The Demonic Tome'! And the weirdly altered demonic adventurers are the perfect NPC villains for a group of 
'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan PC's.  The Earth shudders under the weight of the books of Pandomonium. The doors of Hell have been flung open & only the PC's can save their Earth! The demonic hordes lead by other adventurers come to call. 

There are a few  areas where the invasion could begin San Fanscisco, New York City, The Saint Loius arch, or Los Angeles. These ares are iconic & have urban legend credit when it comes to having gate ways to the bowels of Hell itself. For handling the minor incursions of the diabolic & demonic use the demons & devils from the D&D Rules Cyclopedia (Basic). This will give the players a touch stone with their old school roots. 

Then unleash the hordes of Hell from Rafael Chandler 's Demonic Tome! This might be a perfect way to have the PC's explore an Earth that literally teiters on the edge of Hell itself. 

Monster A Go Go - Elf Lair Games Veterans of the Supernatural Wars Rpg By Jason Vey & Tomothy Brannan Session Report & Monster Workshop

"We Are the Night Shift...
We alone stand against the vampires, werewolves, and Things that Go Bump in the Night.
We know the things that prowl the shadows, the monsters that feed on the innocent.
We have seen Something Weird.
We control Something Weird
We create Something Weird.
We study Something Weird.
We are the things that Weird Things fear.
We are the Weird.
We are the Night Shift, and we are all that stands between you and the end of all that you know."



'Veterans of the Supernatural Wars Rpg' by Jason Vey & Timothy Brannan is one of those OSR games that quietly always finds its way back into my hands especially for designing modern OSR adventures. 

DM Steve & myself find ourselves looking at several OSR monster options for our on going campaign. One of those OSR lights that we're currently looking at is Rafael Chandler especially Lusus Naturae & the Chapel Wights who fit the asthetic of the on going campaign. 


The PC's have crossed swords with a butcher priest & things went down hill from there. This week sees the PC's starting in on the dungeon of Ben Laurence's 'Through Ultan's Door' issue number two. The PC's have dealt with the weirdness of the  Dreamlands. 

"Through Ultan's door in this second issue into the Catacombs of the Fleishcguild, a 31 room dungeon for a party of 3-5 characters of 2-3 levels in Advanced Labyrinth Lord or any older edition of D&D. The Catacombs are replete with the fiendish traps of butcher priests, blood demons, muscle jellies, flayed heretics, and much more. This 36 page zine also has articles on house rules for playing in slumberland, on the undead of Wishery, and ib new spells and magic items."

The Fleishcguild, are major NPC faction  within the ongoing campaign. The PC's last week dealt with a traveling saleman NPC being killed by a muscle jelly. And they found Fleishcguild gear within said traveling saleman  NPC's apartment. 

And they found a strange arcane design under the bed of the traveling salesman. This design was a gateway into  the Catacombs of the Fleishcguild. But this section of the Dreamland was a perfect spot to add in the Advanced Dungeons & Dragons Fiend Folio monsters into the mix. 


This area is full of ruins & underground areas infected with blind helms & worse. The question is while the PC's are dealing with the dungeon could monsters make their way back across the planar threshold? Ancient OSR theorists say yes! 

Christmas Carnage - Thoughts on WG4 The Forgotten Temple of Tharizdun & The Cults of Tharizdun For A Modern Day OSR Campaign.

 It has many names The Dark God, The Ender, He of Eternal Darkness, the Ebon God, the Black Sun, the Patient One, He Who Waits, the Anathema, the Father of Elder Evils, the elder elemental god, the Author of Wickedness, the Eater of Worlds, the Despised, the Undoer, the Chained God, the Chained Oblivion & it has made the crossing. Since dealing with both my Castles & Crusades Wilderlands of High Fantasy & Victorious rpg campaigns. Veterans of the Supernatural Wars rpg has generated a ton of interest among my players. So an old campaign notebook entry reared its head. Could the cult of Tharizdun present a dangerous and viable threat within a modern day Earth?! "WG4 The Forgotten Temple of Tharizdun was written by Gary Gygax and published by TSR in 1982 as a thirty-two page booklet with two outer folders; there are no modules with the codes WG1-WG3. ", this is the publication history that we all know. 

We know that the release of Iggwilv & her daughter is going to create two cults at least upon the world both demon worshippers & a vampire cult. But the greater evil maybe lurking in the background of the campaign yet to rear its head & that's Tharizdun. 

Iggwilv is one of the keys to this & to this end I've placed an alternative version of her temple from S4 The Lost Caverns of Tsojcanth within  Maple White Land. Her black witch covens would have spread across South America, the lower half of the United States, & even up into the New England States. Why?! Her description gives her ambitions as not being seditary at all; "Iggwilv is said to have two forms, one of which is that of an old crone (said to be her true form), and the other, a human female of dark beauty. In the latter form, Iggwilv has long black hair and pale skin. It is said none who have seen her in her true form still live.^[16]

She has many alternate names. On Oerth she has been called the Witch Queen of Perrenland and the Mother of Witches. She is known as Louhi on one alternate Prime Material Plane world, and as Ychbilch on another. Those close to her sometimes address her as Wilva." 

The real goal would be to suck Earth dry & then move on while releasing  Tharizdun. What would slow both Iggwilv & her daughter would be the fact that they don't share power easily with one another. Gary Gygax's version of Grayhawk had Gord The Rogue travelling the planes as a champion of Balance after a new cat lord was inserted into his place; ""Evening Odds" appears as story 14 in Pawn of Chaos: Tales of the Eternal Champion, an anthology of fiction inspired by Michael Moorcock's Eternal Champion mythos. The story takes place some time after the events of Dance of Demons. Gord has apparently been deposed from his position as the new Catlord and is traveling the alternate realities as a Champion of Balance. In the course of the story he upsets a plot by the archfiend Baphomet on modern Earth." 

This places Gary Gygax's Greyhawk near to the Prime Material plane.  In fact that it also places The Wildlands of High Fantay near the planes Prime as well.
 Several magazine articles in Peagus magazine the Judges Guild house magazine have the Wilderlands cross over near Earth's sphere. This very idea makes Earth a prime hunting ground for a number of Dungeons & Dragons monsters. 

Tharizdun might already be touching a piece of the Earth's plane within this campaign world version of  WG4 The Forgotten Temple of Tharizdun. The cult of Tharizdun would rely on its inner circle members to be nilistic & dangerous undead fantics. Fanatics who would do anything to further their various masters agendas. There are plenty of idiots who would fall for the false promise of immortality that undeath brings. So the ranks of these cults would swell like a disease sweeping across the world. We've seen this type of event time & again within our modern world. Right now its just spit balling ideas out here: 

1. A party of adventurers is brought together from  across the planes & Earth by the powers of the Balance to stop the destruction from happening. 
2. These cults go to war against one another because of each one wanting to seize power.
3. Those who make a cross over unto Earth risk being stuck here for the rest of their lives.
4. The powers that be use Earth as testing ground for young adventurers. 
5. The hidden & lost places of Earth allow one to cross over into Greyhawk & the Wilderlands. 
6. The minor gods of the Wilderlands can have influence on their agents on Earth. 
7. The occult & the supernatural are a cancer on the planes allowing Chaos & Law to gain foot holds that cause the planes to go out of balance. Thus bringing in exterterminators to hand the problems. 
8. The Gord The Rogue novels show a clear campagin path to bring in classic D&D elements into a campaign setting. 
9. Greyhawk has some excellent campaign points to exploit for the player's PCs & they won't be expecting it. 
10. Standard D&D magic may be much more dangerous on Earth.