Benjamin Washington, also known as "Knox", was a criminal who was among the escapees from Level 5, and was eventually recruited intoPinehearst Company. He was an evolved human with the ability to feed off people's fear and turn it into his own incredible strength.
The Second Coming
While in Noah Bennet's house, Sylar, while stalking and hunting Claire throughout the house, finds a collection of evolved human files in one of Noah's boxes, one of which is on Knox. Sylar remarks the files are a "shopping list" of new abilities, and intends to take Knox's ability, as well as those of the other prisoners.
While in his cell, Knox, kept in a straitjacket, paces back and forth repeatedly.
The Butterfly Effect
When Sylar does arrive, Elle Bishop ends the battle by unleashing a massive discharge that blows out Level 5's power grid, releasing a dozen prisoners. Knox gathers some together, including Jesse Murphy (inhabited by Peter Petrelli), Eric Doyle, Flint and the German, and leads them to escape Primatech Research.
Much later, the group has arrived at a gas station, where Knox and the others take their time murdering the other tenants. Knox stops Peter from calling Nathan and directs him to the car the German secures for them. Knox then convinces "Jesse" to come with them and escape, as sirens approach.