I know one on earth which involved a ?? Knight hidden in a cliff. You had to lure it to the edge then jump away and hope that it fell, and inside was a chest(hidden usually in ceiling rafters or just in a corner) and a dead ghost just sat in the small to to the left at eye level. The cliff area is near the huge hive spire/crashed ship thing and from there to the area where all the fallen spawn out of a cave near the wrecked helicopters. Hope this helps! :)