almost forgot, henchmen have access to special traits:
+1 army strategic regen
+10% xp
+5 armour
forget if there was a fourth, don't think there is.
you can creat your own henchmen now and pick your three traits so you can take 3 magics or 2 magics and a trait, or 1 magic and a trait.
i like to take life magic, muscle, for +1 damage and then something else if i have access to books to grant elemental magic
