Originally posted by grapplehoeker:

Dump Frostner and forget about Eikthyr power
Forge a silver sword and upgrade it to the max.
Use Bonemass power.
Get up close and personal and then use the sword's secondary attack and then swish, swish, swish and repeat... you'll kill Yagluth in no time ;)

Frostner works for me. Killed Yagluth 12 times already with the same weapon. Swords kinda meh tbh.