Yag is weak to Spirit and Blunt so Frosner is a good choice.

I saw a video where someone took him on with 100 wolves and 100 lox. It was epic. The first time they took him down in about five seconds. They just swarmed over him.
They kept summoning him over and over. After about four of five times, the army was getting thin and he was lasting a few minutes. Eventually it became a regular Yagluth slugfest.