The giant Thiazzi
Under the command of Idunn, you move to attack Thyrmheim. Upon entry, you find signs of Sigmund's assault.
Note* Youthful Idunn is an ally in this battle.
At this point in the game you will need to have good skills on your units. It's still not too late to begin doing that. The important skills to have to pass this dungeon are those that 'counter':