Multi-Finisher is a starting Combat skill that lets you finish off up to four badly hurt enemies in one move. It is how you end crowded street fights quickly and bank extra XP.
Multi-Finisher sits at position 1 of 18 in the Combat tree. Multi-Finisher costs no skill points. The twins learn it during Sequence 1. Jacob and Evie each have their own skill tree, so you buy Multi-Finisher once for each twin.