Sangre is the mysterious unidentified 'wolf' who resides in a titanic cave. Not much is known about her past apart from the fact robots killed her parents. As a teenager, she seeks her revenge by hunting down every robot in existence. Her first appearance was in the crossover fighting game Sangre.
As mentioned earlier, barely anything is known about her past. There have been some theories going around in the character diaries in Sangre though. The most basic one is in Coldilocks' diary where she says 'She was born as a normal average wolf doing normal average wolf stuff. One day, she got hit in the head and went crazy. Sangre stole a gun and seeked revenge for no reason. Yeah, that's stupid'. We do know, though, that her parents are either dead or lost and some robot species had something to do with it.