everything is immune until you destroy the totems in k3k. each totem will take away immunities from a cluster of skeletons and necromancers near it.
tl;dr - kill totems first.
TheUnderling wrote:gg2 said mercs can't equate to an actual player's killspeed and that they have difficulty farming common farming uber. I can understand why mercs can't compare to actual players in terms of speed. I'm still unsure if they are capable of farming ubers on their own at enough speed so that the idea of having a barb stacking mf is good.