Ace, as a puppy, was bought from a pet store by Ronny Boxer who forced dogs to fight one another gladiator style for the amusement of paying crowds. When the police busted Boxer's game, Ace escaped this abusive, violent life. He wandered around Gotham for a while and soon found Bruce, a fellow tormented soul, who was making his yearly pilgrimage to the spot where his parents died. Ace attacked a Jokerz about to attack Wayne but was injured. Wayne saved him and brought the dog to his home, since then Ace had become Bruce's constant companion as well as something of a guard dog. Young Terry McGinnis, Wayne's assistant and protege, seemed to be the only other person Ace ever connected to.
Although Ace typically does not accompany his guardians into the field, the dog is often an asset when he does. For instance, his species' acute sense of hearing and smell and fighting experience are considerable assets. Furthermore, he is extremely strong for his species, capable of throwing a man a considerable distance with his mouth even with poor leverage, able to bite through an electrified manacle with ease and even managed to stand up (albeit barely) after being electrocuted by Joker's well known lethal joy-buzzer (which has been known to knock out grown men with a simple touch).
- Ace might have been named after the original Ace of the Royal Flush Gang.
- Ace's seemingly super-canine strength and durability may be the result of Ronny Boxer testing the effects of Serastone on him. Boxer was known to make heavy use of the artificial growth hormone later in his career and may have been experimenting with its effects on dogs at the time Ace was under his ownership.
- Ace appears to be an homage to Ace the Bat-hound from DC Comics.