The dungeon was created by giants as a planar gate. It was eventually abandoned by its creators, and the dungeon has fallen to ruin and been rebuilt many times since then.
Size
Tiny (35 x 35)
Walls
Hewn Stone (DC 20 to climb)
Floor
Smooth Stone
Temperature
Warm
Illumination
Dark (individual creatures may carry lights)
Wandering Monsters
1
Orc Eye of Gruumsh (cr 2, mm 247) and 5 x Orc (cr 1/2, mm 246); hard, 950 xp; performing an evil ritual
2
Ghast (cr 2, mm 148) and 1 x Ghoul (cr 1, mm 148); easy, 650 xp; cursed to wander senselessly
3
Roper (cr 5, mm 261); medium, 1800 xp; wandering senselessly
4
Drider (cr 6, mm 120); hard, 2300 xp; gathered around an evil shrine
5
Orc War Chief (cr 4, mm 246) and 1 x Orc (cr 1/2, mm 246); easy, 1200 xp; trying to lure the party into an ambush
6
Wight (cr 3, mm 300) and 5 x Zombie (cr 1/4, mm 316); hard, 950 xp; patrolling their territory
Someone has scrawled "The Obsidian Orb is wreathed in flames" in draconic script on the north wall, and a crushed helm lies in the north-west corner of the room
Monster
2 x Hobgoblin (cr 1/2, mm 186) and 1 x Bugbear (cr 1, mm 33); easy, 400 xp