Actually, I'm just guessing... not speaking for the devs. I don't know how hard the ghosts are to defeat in R41, I didn't try fighting them in QA. Personally, I think its okay to make certain mobs handled only or handled more easily by one type of skill or tactic. It makes the game interesting. I'm also guessing certain enchanted weapons help. And would be interesting if a certain type of metal was better against undead (silver or iron). Its a separate thread topic, I guess.