Continuity mistake: When Conan is fighting the half lizard/man monster, the first two times Conan smashes glass panes, you see large gashes appear across each of the monster's pectoral (chest) muscles. Later in the fight the wound on his right pectoral disappears and reappears numerous times.
Continuity mistake: Watch the shot where Bombaata is smashing a hole in the rock wall with his mace-axe weapon. From the outside it appears as though an entire section of the wall is giving way, then the camera cuts to Bonbaata on the inside and he is smashing at a rather small hole in the otherwise intact wall.
Continuity mistake: Two horsemen try to entrap Conan in a net during the opening fight sequence. He rolls under the net, grabs it and gives it a mighty heave, sending both horsemen sprawling, and then drops the net over Valeria's stone altar. A few shots later, the altar is bare and the net is nowhere to be seen.
Continuity mistake: Before entering the room with the wizard leader, Zula tosses the torch into a cubbyhole in the wall, but the cubbyhole isn't lit up by the torch as if it went out (or fell down a shaft). However, when escaping, Akiro grabs the lit torch out of the same cubbyhole, which is lit up by the torch (and he didn't use his magic to relight the torch).