I know it is pure speculation, when it comes down to it. But most discussions seem to have us pegged for the Wind of Beasts being bound to one of our characters. I was wondering what sort of manifestations people think might fit such a character? Its manifestation seems far less obvious than Life/Death/Heavens. Perhaps somehow allowing more beasts to be taken in the army? 'Monsters' count as core? A passive buff to mounts/monsters would be a bit of a cop-out.
Why would the incarnate of beast do such things, when the other incarnates did nothing of the sort? It would probably just be Tehenhauin, either on a big-ass mount, or with an undispellable transformation into some huge ass monster with insane rules. An incarnate that needs to transform would also be leagues ahead of the others in terms of balance, because he NEEDS to transform, and with End Times magic, that can take a while, during which you can be shot to death. Unlike, say, Malekith and his batshit insane rules that makes him near unkillable to anyone without the ability to render his gear useless/destroy it/steal it.
The undispellable transformation is a really interesting idea, and actually makes a lot of sense. My suggestion was more in jest than seriousness. I just couldn't think of anything logical. The previous incarnates all seemed to just make sense.. a bit like your thought. I do hope it isn't Tehenhauin though - at least not without an update to both his normal model AND the large transformed version. I was sorely hoping for Kroak or Mazdamundi, but neither seem to fit the lore.
I think the new Head of the Empire wizards, Martak, will be the incarnate of beast lore. He was prominent in the Glottkin book and has done some very heroic things to save the land of men recently.