Subject 18 was primarily shown exclusively to the story New Divide. He is a bear, who uses a pair of experimental gloves that he had taken from Trinity Facility after having escaped. His real name, as found out by Trinity is Lars Ulter.
He was first seen in one town, which had not been given a name which is where he took on Rhino in hand to hand combat. He was able to actually stand up to Rhino, thanks to the nanotechnology that was within his system, which in turn, gave him accelerated healing, making him a rather tough opponent to take down, to the point in which he succeeded in stopping Rhino, by knocking him down an elevator shaft.
However, after Terror Squad had lost track on where Subject 18 had ran off to, they headed back to the facility to track him down once again.
Sure enough, the group had found him there, to which Suybject 18 took on Icarus first at the church, yet, he was outwitted by him and soon, found himself face to face with Marcus. After taking on Marcus for a few moments, he in turn, took on Rhino once he had arrived.
After some time, Terro Squad made their way to the local power station, where they had one last stand up against Subject 18. However, after he was standing his ground up against both Marcus and Rhino, he was injected with a mysterious antidote, which caused him to loose his healing ability.
Yet, even after he had lost his ability to heal, he still took on an extensive amount of damage, including being shocked multiple times, stabbed multiple times and shot multiple times before finally beinf killed with one final shot to the head, having finally accepted death in the end.