How to Kill an Undead Hunter

The necromancer is behind all the missing children or the missing disappear. We might want to interrogate him, but that's up to us. He stumbles backwards and says, protect me, my undead minions. Your life force shall fuel my power and your corpse shall serve in my army. All right, our hippo who's now hippo would be up. What do you guys think guys? Fuck him up kill him.