dont know if that was fixed already, if you enter onyxias lair leave and re-enter it will spawn a copy of onyxia and so on, i went so far as to make the game lag just for testing reasons, it seems there is no sprite limit which could cause the game to crash if someone took it too far, if u start the fight after spawning too many onyxia and die, your game will glitch out leading too some funny visual bugs