Captured as a demonic offspring by the Requiem Brotherhood, Shadowclaw was held in chain in the Requiem underground Catacombs waiting to be "judged", until Aaron and his thieves anesthetized the beast with soporific darts and bring it out of the dungeons with an intricate and perfect plan, without killing any Requiem in the process.
It took years for Aaron to bond with the beast: Shadowclaws tried to kill his savior every time he tried to approach to tame him in the beginning, even losing an eye in the process.