Well actually that is well-known to community.
You're able to save 3 out of 3 prisoners from Bloodmoon vaults
really? how do you save the lizard?
oooh yeah, i was more about you can complete Ghosts guarding levers quests more than actually "saving" possesed characters.
You can save the kid and the dwarf, the lizard is just idiot, there is no other choice than killing him.