|The following is based on Fallout: Brotherhood of Steel and has not been confirmed by canon sources.|
He is a mad man who uses a very powerful weapon, a turbo electric plasma rifle, to kill his opponents. When, and if, the Initiate of the Brotherhood of Steel defeats all other combatants on the arena, he fights the Wasteland Stranger as the final challenge, worth of 50000 caps. The stranger says no words, and is probably not only kept alive by the Church of the Lost to fight on the arena, but also enjoys it.
Behind the scenes
The wasteland stranger is also an in-game nickname of Vault Dweller, who also appears in the game. Moreover, this character uses almost the same game model as the Vault Dweller.
Wasteland Stranger appears only in Fallout: Brotherhood of Steel.