I'd never really given these guys a look until this morning. The idea of their biological creature experiments was stupid to me (though the same thing works for the Daelkyr, dunno why), and so I just ignored them.
Actually took a look at it today, and I thought the Zern itself was quite interesting. It reminds me of the Uthraiki from Unapproachable East. It can assume humanoid or monstrous humanoid forms, and can grow to large size. It also has fast healing. Instead of a claw/rend attack, it has a magical attack (melee or ranged, NOT a touch attack) dealing 4d6+2 damage
I'm thinking of using them as a variety of troll (broad Norse use of the word) for my viking game.
Anybody used these before? How do they stack up in a fight?