Was trying out Kruarg the Dread and when I cast him for the final damage on the enemy anointed one, it summoned an Evolved Gorgotha.
I know it was an evolved Gorgotha because it had WAY more Hp than my own and It has a 15 any mana spell. Was only able to get a cap of the reward screen. http://images.akamai.steamusercontent.com/ugc/492403625776206678/DF692E516E4D4566AB82790DC1DB74395A3E311C/
Not complaining but kinda nice to be able to summon an uncollectable troop.