Your favorite Fortress hero.

I think the best hero for the Fortress faction is Helmar. Taking the Secrets of Light skill: 5 Fireballs, and the Light spell at level 20 always adds a significant amount of damage to the overall attack, and combined with magic skills at that level, it's at least +15 to attack, which is very good. Add spellcasting, and you have a very good mage. And with his attack bonus, the creatures have incredibly high attack power, so overall, it's great.