Krimm Blackleaf. Now that is a name I've not heard in a long time.

For this beastie, I'd say he's got the oomph in a straightforward brawl to merit CR20, but his defenses are lacking against anything that doesn't just come right up and try to melee him. His Perception is low enough that anyone with a decent stealth investment and a ranged weapon is going to give him trouble. He can't fly and his ranged options are fairly short. Perhaps most glaring of all is his abysmal +13 Will save. Non-mind-affecting Will-save spells are going to ruin his day, such as Plane Shift, Imprisonment, and Trap The Soul.

Perhaps he could do with a splash of Diamond Mind maneuvers? Hearing The Air and Moment of Perfect Mind would go a ways to shoring up his defenses. Of course, the more straightforward thing would just be to give him passively improved animal senses (he's sort of animaly, so its not unjustified) and a Will bonus. But martial disciplines are fancier.