Originally posted by jonnin:

seekers die in one good hit, eg middle mouse for mistwalker, or if they are unaware/confused and you get a backstab hit. Inside or outside her arena. In the arena, they are summoned in closer to you and maybe didn't reorient/retarget you and go into combat mode before you capped them, making them take the extra damage. If you somehow got them wet, water ups frost damage a lot.
fire and frost work well, as does just stabbing her. With the root chest and poison resist she is fairly soft hitting and anything works to chew her health down.

Sure but she's dead now. The question is can you destroy the boss respawner? It seemed to take damage and I didn't want to test it