BT-001, orBaboon Tumoras it is unofficially called, is a improper and very unstable tyrant mutation that inhabited the Arklay Mansion laboratories during the 1998 Arklay Mansion incident. Out of all the animal test subjects that Umbrella labs received(Great White Sharks, Dobermans, Snakes), a lone olive baboon was delivered. Most likely a shipping accident it was unsure what was to be done with it. It was later given to a lone scientist who took interest in the primate. The scientist did whatever he pleased with experiments on the creature, never conducting a proper study with a outcome, instead using him as a guinea pig. B.T. was used to test almost every type of virus strain they had at the labs. The mixture of samples injected into the baboon resulted in horrific mutation and size growth.

In his current form, B.T. is a large mutant with various animal genetic traits, most unknown. They are suspected to be reptile*,* amphibious and insect genetics. Due to the large amount of mutations he underwent BT is mostly walking rotted flesh. His skin hangs off his frame in gross, flabby fluid-filled rolls. His back feet and front fingers are covered in a thick keratin covering that resemble reptilian feet. His lower stomach sports a similar thick armor plating, formed from his intestine which burst outward and hardened. His skin is splitting and rotting in various places leaving his bones protruding with growth spines on his elbow and ankles. The trademark white tendrils have bore a hole in the side of his neck and is suspected to be taking over what remains of his brain.

B.T.'s spinal cord is shoved through his back. The wound has resulted in a split of flesh going down his left side. He is constantly seeping fluid of some kind.

Lacking a tongue, the tendrils act as aid of pulling victims closer to his jaw so he can consume them. He reportedly smells of rotted flesh, fish and bile from the constant stream of it and drool that emits from his mouth. B.T.'s large powerful tail is made up of his intestines which burst outward and reformed. A large fleshy mass resembling a umbilical cord supplies constant blood flow to his powerful tail. The most noteable feature of his tail is the insectoid stinger which has spines made from insect scopulae. B.T. is completely blind so usually charges in the general direction of any sound and hope he gets you. His eyes seem to assist in detecting movement.

B.T. has strange hatred for Chris Redfield for unknown reasons, choosing to chase him down even when others are present.

The creature eventually meets his end at the hands of Chris Redfield and a rocket launcher."