1d20 Random Unusual Adventure Locations in Underborea Encounter Table

Within Hyperborea there are places that men should not go, these places are rarely visited by adventurers who might live to tell the tale. These adventure locations have their own unique character as well as dangers. Visit these at your own risk my friends.

Deep under Hyperborea there exists another world of adventure, dangerous byways, and other worldly sites of weirdness & deeper strangeness. A world of its own rules, laws, forbidden dangers & much worse the further down into the interior of this ancient place.
"I can picture that party fishing up unhallowed secrets & blasphemous palaeogean artifacts from those monstrous arcades & Cyclopean unlighted crypts."
From A Letter From HP. Lovecraft To  Clark Ashton Smith

"As to the difference in our respective styles or moods—one thing that influences mine is my extreme & lifelong geographic sensitiveness. I have never been tremendously interested in people, but I have a veritably feline interest in & devotion to places. The greater number of my dreams & visions are fantastic syntheses, etherealisations, & rearrangments of the landscape & architectural impressions which impinge on me during waking hours; & during those waking hours there is no pleasure which can compare with the experience of seeing strange old towns & houses & scenic vistas. These things are, & always have been, the most potent stimuli my imagination can possibly encounter; hence they usually form the points of departure for my excursions into the outside cosmic gulfs. Like Gautier "I am one for whom the visible world exists"—though my chief use of the visible world, unlike his, is simply to provide a springboard for leaps into abysses & dimensions forever beyond visibility.

Yr most obt & hble
HPL"

1d20 Random Unusual Locations in Underborea Encounter Table 

1. A strange ancient altar chamber carved out of the rocks itself, this chamber is in the shape of a giant serpent & rhyme with age as the blocks are stacked and carved by smaller then human hands. 
2. The carved stair way where a serpent man whispers weird secrets in the darkness to some unseen presence. There are 1d6 ghosts of alien creatures hovering around him. 
3. A monstrous arcade of stone & carved rock that contains three acres of a hideous black pudding at the center of which is a single penis shaped rock with row after row of alien carvings  
4. Four acres of caverns choked with tons of prehistoric bones & gold nuggets of fist sized under the bones an ancient creature swims through them. 
5.  A giant totem animal carved into a twenty five foot wall in the shape of a seven fingered clawed hand. 
6. A giant skull of some long lost god now a part of the cavern systems the brain of the god forms the ecological network of the caves. Each creature within represents the ego, id, etc. of the god thing. 
7. Four hundred ghosts of aliens long removed from the upper world are here in the underworld going through the motions of living. The caverns, galleries, etc are filled with their perfectly preserved upworld buildings and such. There are tons of relics and unusual finds here. 
8. A Roman galleon crewed by undead sticking out of a chasm wall. 
9. There is a chained demonic ape thing that screams in its cavern for freedom but can't leave for the wizard that summoned it is long dead. The thing will answer any questions put to it but every tenth question it will curse the questioner. It guards a long lost treasure of Hyperborea.
10. A fully formed Hyperborean sky ship is caught in the rock & it still has power but there is an evil alien presence aboard along with 1d20 undead or zombies. 
11. A half demonic gem seller is making its way to nearby serpent men settlement, it has over a thousand enchanted gems but it hates humans with a passion. 
12. This volcanic cavern is the home to over 1d8 fire elemental monsters who forge the chains of the gods. They will welcome a game of riddles but will lop of a limb for any wrong answers but will reward with a gold nugget for right ones. 
13. This place is the home to the black mirror of the Outer Darkness and will open upon several unusually dangerous planes of the Outer Darkness or the Abyss. 
14. Here within this cavern is a perfectly preserved sky scraper from Old Earth with its power still running and the ghosts of its occupants unaware of their fates. There are lots of valuable artifacts here. 
15. This cavern is filled with thousands of zombies embedded in the walls each is a part of an alien hive mind. 
16. A colour out of space makes its home here and has warped the stone walls here with weird radiations and forbidden realities. Anyone entering here will have to save vs death or be warped in and out of the local space time. 
17. This cavern is the home to layer after layer of weird crystals that are actually the mind and memories of an extinct god. Taking any crystals from here will activate the invisible stalker 'white blood vessel' guardians. But each crystal stores 1d8 minor spells of black magic, these crystals are worth 700 gold pieces each. 
18. A strangely wrought temple complex is the home to several minor Great Old Ones who feast upon the reality and flesh of those who enter here. These caverns are rife with the ghosts of their victims, for this place has become a pilgrimage sight for those of demonic worship but they don't understand what they worship. 
19. Here the entire cavern is the fossilized remains of an ancient star god preserved in stone. Its power manifests as phantom ghostly presences and create strange sanity shattering illusions for which this place is sought out for by black druids of the underworld. 
20. A huge vault of stone holds the organs of thousands of Elder Things which form a network of dangerous alien intelligence. Anyone entering here must save vs magic or become connected to this alien bio computer of incredible age. They're mind will be merged here and they may fall over dead as their mind is absorbed. But there are strange crystals that hold thousands of years of knowledge here.