And how would he use his powers if there isn't anything dead around? It's just better to choose another one.
He just has to make them dead, the good ol'fashioned way :D
Rata-tat-tat!
Basically, he can sort of buff using essence (i.e. escaping life energy from the recently dead).
Unfortunately, the early "buffs" are very much temporary. It's not useful at all at the beginning, except in select situations, but once he gets the hang of it, we get passive perma-buffs. It's ridiculously OP if there are lots of fresh corpses. Not so useful otherwise.
That's why it's great! It gets more and more useful the further we go, we may just have to deal with uh... baggage early on, (I beg your pardon).
Actually, depending on the size restriction, it might be a little OP. Lots of snakes y'know? Then again, depends on how much essence he gains, and how much it takes to "buff" the group.
It's a 100% support skill! Like healing!