Chivalry was the favored stallion of the Last Hope garrison commander, a marrowborn member of the Luminatii Legion named Vincenzo Garibaldi. A thoroughbred, the stallion is described as "black as a chimney sweep's lungs" and stands nearly twenty hands high. Chivalry was supposedly treated, and fed, better than most of Garibaldi’s men, and tolerated none but his master's hand.
That said, Chivalry greatly objected to and violently protested his theft at the hands of Mia Corvere in Nevernight as a means to cross the Ashkahi Whisperwastes and seek the Red Church, and, as punishment, sought to make her life a living hell. He partially succeeded, enough to earn the moniker "Bastard" from the girl. Their parting upon Mia's initiation as an acolyte was a glad one.
However, despite their supposed enmity, much later on in the novel, when Mia's need was dire, "Bastard" came to her aid, saving not only her life but the lives of the Red Church Ministry, greatly improving their relationship. The two are in a much better place now, Mia even reminiscing fondly about the stallion during Godsgrave.