Another one, this time at the end of chapter nine. He will appear right after you solve the puzzle. He's fighting alongside two wolves. Kill the boss first, then the wolves. Use attacks that damage all enemies. Robert i Tristis are recommended for this fight. Robert's arrows can hit all enemies and slow the cooldown of their turns.
Tristis can protect his friend; also, the cooldown of his turns is shorter with each attack. This allows him to stop enemy attacks more often. The wolves can also slow down your turns. The boss deals massive damage. If any of your warriors dies, replace them with another one, for example Tristis for Rubella and Robert for Oegnus.