Soooo.... Grapevine yay?
The Abhorrent I threw at the players in Episode 4 was a variant-of-a-variant, in essence an Ever-Vec that prolongs its existence by blight-grafting (Ganglia-style) fresh body parts to itself in order to keep the Blight animating it Hot. Like most Abhorrents, the origin of the Chimaera is unknown; speculation has placed it as either an experiment gone wrong (thanks, DHQS!) or what happens when a large number of people go Vector within a short timeframe and one (or more) are taken down while close to a mobile vector.
As the pieces decay, it will shed them in favor of grafting new appendages. This means that the Blight is always considered Hot, and the Chimaera functions on the same level as a Vector in terms of intellect; as it always has a minimum of one fresh brain, the Chimaera is even capable of rudimentary ambush tactics and a modicum of intelligence. As it increases in mass, however, it becomes slower as the sheer size of the creature impedes its movement.
Due to the nature of its flesh, it should be treated as though it has additional hitboxes equal to half the total of amalgamated body parts for that particular hit box (i.e. 3 extra left legs will give the Chimaera 15 extra boxes on the left leg; 2 additional heads will give it 10 extra boxes on the face.) The Murder Modifier for the creature is treated as 1+(1 for every 30 additional hitboxes) for the purposes of damage only; speed is equal to 4- Murder Modifier to a minimum of 1.
No two Chimaera look alike. The ways they Blight-graft additional flesh to themselves vary so much that in their own way these things are fleshy snowflakes, each horrifically unique. Some will layer flesh over flesh, building armor-like structures. Some will extend limbs, some will opt for multiple limbs. Describe them in whatever body-horror-inducing way you wish, they will function similarly. Longer limbs might give the creature reach, thicker hide may give it a modicum of armor; it is entirely up to the Market to decide the level of Cronenberg
A Chimaera can be killed by completely depleting the hit boxes of head or torso. Destroying all of a set of leg or arm hitboxes will slow the beast down- until it adjusts to the new Murder Modifier.
When in danger, a Chimaera *might* shed the outermost layer of flesh in order to flee; in this case, it will return within a session to attack the party again.