I was just thing of using Mr. Slime ball in that picture. No humanoids, just some physical abomination that doesn't conform to familiar things.

Image:
[img=http://www.fightersgeneration.com/np5/blaz-cs/art/arakune-cs.jpeg]
Name: Black Beast "B.B."
Age: Said to be a fairly new Grimm, oldest record of it's existence dating back only ten years.
Gender: Referred to as male
Race: Grimm
Weapon: It's entire body is a weapon, thanks to it's veritable shapeshifitng abilities. Commonly it can produce a neigh infinite amount of bone-like appendages adorn with blades, claws, spikes, and other instruments of death. It can also release a noxious cloud which is not only toxic to most creatures, it attracts Grimm from near by. Additionally, the Black Beast is capable of housing and controlling an entire ecosystem of poisonous insects that rest inside his body, some as small as bees and others as large as dogs. It can also cloak it's body to prevent light from reflecting off of itself, turning it invisible. The Black Beast is very agile, who's speed is often a match even for those with a speed-based Semblance. Also it can talk (using other people's voices).
Color: Blood-soaked coal.