Zivah only has healing skills and a limited Manapool... she isn't much of a fighter at all, Erevi atleast knows some fire and lightning skills... and after our exploration of the Cult (as in Sect) of death probably also some dark skills.
the Succubus is a temptress and posses some fire attack skills... still she self admittendly is for love not war.
The Familiar was attached to the MC and is feeding upon his power, the initial ritual to bind the 2 probably took some Power from Nergal but after that it's the MCs task to keep her alive (likely also a reason why she is so goddamn horny
).