Can Adventurer, Conqueror, King Rpg Second Edition Rpg be used with original Dungeons & Dragons rpg ?!

 Yes, absolutely. In fact, Adventurer Conqueror King System II (ACKS II) and Original Dungeons & Dragons (OD&D) share the exact same mechanical DNA.

Because ACKS II is built on the foundation of the classic Basic/Expert (B/X) tradition—which itself was a direct stream-lining and evolution of OD&D—the two systems are highly compatible. You can easily lift elements from one and drop them into the other with minimal friction.

Here is a breakdown of how they cross over, where you will find the most value, and the few areas where you'll need to do a little quick math.

1. Where They Lock Together Perfectly

Because both systems use the same foundational "Old School" math, several core components require zero conversion:

• The Six Ability Scores: Strength, Intelligence, Wisdom, Dexterity, Constitution, and Charisma operate on the same 3–18 scale.

• Core Combat Stats: Hit Dice (HD), Hit Points (hp), and the concept of Armor Class (AC) function identically. If an OD&D monster has 3 HD, it translates perfectly to an ACKS II 3 HD monster.

• The Scale of the World: Movement rates, ten-minute dungeon turns, and one-day wilderness turns are completely synchronized.

2. The Best Ways to Combine Them

Most GMs who marry these two systems do so to fill the specific gaps each system has.

Using ACKS II to Supercharge an OD&D Campaign

OD&D (especially the 1974 "Little Brown Books") is famously loose and relies heavily on referee rulings. ACKS II is essentially the ultimate simulationist toolkit for that exact style of game. You can use ACKS II to provide:

• The Endgame (Domains & Kingdoms): If your OD&D characters reach high levels, OD&D gives very loose guidelines for castle-building. ACKS II gives you a flawless, mathematically airtight economic engine for investments, land management, taxation, and garrison costs.

• Trade & Commerce: Use the ACKS II mercantile rules to determine market classes for OD&D settlements and run trade-route campaigns.

• The Proficiency System: If your players want more distinct customization than OD&D's minimalist classes allow, you can overlay the ACKS II proficiency system directly onto OD&D characters.

Injecting OD&D Flavor into ACKS II

If you prefer the robust engine of ACKS II but want that weird, open-ended, high-fantasy 1970s flavor:

• Adventures and Monsters: You can run classic OD&D modules (like In Search of the Unknown or Keep on the Borderlands) using ACKS II rules. The stat blocks can be read straight off the page.

• Magic & Spells: You can introduce OD&D’s specific, sometimes looser spell interpretations into an ACKS II campaign as "lost" or "ancient" magic.

3. The Minor Friction Points (How to Fix Them)

While they are highly compatible, you will run into a few mechanics that don't match up perfectly. Here is how to smooth them over:

Ascending vs. Descending Armor Class

• The Friction: OD&D uses Descending AC (where AC 9 is unarmored and AC 2 is plate armor). ACKS II uses Ascending AC (where AC 0 is unarmored and higher numbers are better).

• The Fix: To convert an OD&D Descending AC to ACKS II Ascending AC, simply subtract the OD&D AC from 9.

  Example: An OD&D monster with AC 4 becomes AC 5 in ACKS II ($9 - 4 = 5$).

Attack Matrices vs. Throws

• The Friction: OD&D uses a combat matrix chart to look up what a character needs to roll to hit. ACKS II uses an "Attack Throw" target number (e.g., an Attack Throw of 10+ on a d20).

• The Fix: Use the ACKS II class progressions for combat. If you are importing a unique OD&D monster, look at its Hit Dice, find the matching Hit Dice row on the ACKS II monster attack table, and use that target number.

Saving Throws

• The Friction: OD&D uses five classic saving throw categories (Death Ray/Poison, All Wands, Turn to Stone, Dragon Breath, Spells). ACKS II streamlines these into five slightly different categories (Blast, Death, Gaze, Petrification/Paralysis, Spell) based on class.

• The Fix: Just use the saving throw values of the closest equivalent ACKS II class or monster HD. Don't sweat the structural difference; they cover the exact same mechanical hazards.

The Bottom Line: You don't need a complex conversion guide. If you treat ACKS II as the "advanced mechanics manual" for the world simulation, economy, and mass combat, and use OD&D (or its modules) for your core dungeon-crawling and class flavor, they fit together like glove and hand.