Krieg the Psycho is the second (and final) DLC character that was added to Borderlands 2, becoming the sixth overall playable character in the game. He was released on May 14th, 2013, after being initially revealed on March 24, 2013.
Krieg wasn't always the crazy killer he currently is, with a voice of his former self in his mind telling him to kill the people who deserve it, as well as help others. If Krieg would ever kill an innocent, the inner voice will take control of his body and punish both by killing himself. He was almost killed by a train, which is when he ran into another Vault Hunter by the name of Maya. Recognizing her powers as a Siren, the inner voice in Krieg's head told him to join up with her.
Unfortunately, the only words to come out of his mouth were "I'm the conductor of the POOP train!". Of course, due to this, Maya started attacking Krieg and failed to notice the bandits approaching from behind. Eventually shouting out the danger to her, Krieg starts slaughter the Rats and receive some help from Maya, with her softening up to his demented self. He ends up in Windshear Waste after hanging on the side of the train that the Vault Hunters were on.
Krieg's action skill is called Buzz Kill Rampage and offers a few benefits whenever he triggers it. By pressing the fire button, Krieg will swing his buzz axe and throw it if you aim and then fire. His melee damage is increased by 500% and he will regain all of his health upon killing an enemy, as well as having an increase in his movement speed by 33% This state lasts for around 15 seconds and the initial cooldown is 120 seconds, but it get reduced by taking damage.