All 3 games share the same basic mechanic,
But each has it's own twists. Yup, IOD2, DOD and AOD.
IOD2 is simpler and quicker than DOD (IOD2 has a Flash game version, try it!), DOD is more complex (full blown 1+ hour dungeon crawl game), and AOD is the multiplayer version.
Meanwhile, IOD has different mechanic (using a die).