Clayface's most common origin story is that he was an actor who was on the edge of losing his career. He was forced to use an experimental cosmetic cream which later had dangerous side effects. In combat Clayface will often change his fists into hammers, swords, and spikes. He also uses shape shifting abilities to impersonate other people and has often shape-shifted into the form of many of Batman's enemies.
Batman: Arkham Asylum
Clayface made a cameo in the 2009 game Batman: Arkham Asylum. Clayface (Basil Karlo) appeared in the asylum locked in a cell with a sign saying "Danger. Do not approach. Inmate may be impersonating other personnel." next to it. Clayface uses his shape-shifting abilities to try and convince Batman to let him out, and shape-shifts into Aaron Cash, Warden Sharp, and Commissioner Gordon. If Batman finds all of the Arkham chronicles Clayface will also inform him of Warden Sharp abruptly leaving the asylum despite Batman telling him to stay hidden. In the game Clayface's psychological profile notes that he may have multiple personality disorder and identity disturbance.
Batman: Arkham City (GAME RUINING SPOILERS)
In a VERY SPOILER-Y appearance in Arkham City, Clayface is an integral part of The Joker's plan to take over Gotham. His role in the game was infamously spoiled by a thug talking in the Quick Look for the game, and later censored out by the Giant Bomb staff.