Buccaneer's Cave, level 2, southwest area. East room, level 4 of crypts. Dragon's Den in Dungeon Destard. Find the 3 stones and stand in the center. You should be next to an old dead tree, at 59S 50E. Dig in the patch of dirt just south of you.
End game Use human lens on left, gargish lens on right.
Use the move command to place the 8 moonstones in the vortex cube, then place the vortex cube on top of the codex.