
A crazed Psycho with two personalities within him: his clearly dominant bloodthirsty personality and his inner voice who acts as a conscience... the inner voice is in fact who Krieg used to be. The result of horrible experiments by the Hyperion Corporation, Krieg's mind was completely destroyed, causing two personalities to reside within the same body. Krieg managed to escape the facility, and the inner voice keeps Krieg under control by having him avoid killing innocents, only the 'deserving' to satisfy the new personality's lust for violence.
Krieg's strength comes from the fact he can become a berserker at any given time, rampaging through enemies with his buzz-axe. When his shield is down, his body is actually beefy enough to withstand a lot of damage, and in fact fuels his rage, making him dangerous.
Krieg suffers from various symptoms and classifications of insanity, such as schizophrenia, and occasionally suffers from clanging. His sentences usually make no sense, and are usually associated with gore and violence.