Ace was the guide dog of a blind native American named Black Wolf, who just called him "Dog". After helping Batman against some criminals and Black Wolf's subsequent death, Batman adopted Dog and renamed him Ace.
Ace also known as Titus lives in the Batcave and sometimes helps in cases where his sense of smell is useful. He is very affectionate towards Batman. Occasionally, Ace will help Batman or Krypto (the Super-Dog) to fight crime.
Ace was originally used for illegal dog fights, until he escaped into the streets. He found Bruce Wayne, who was paying respects to his parents when one of the Jokerz attacked him. Ace saved Bruce, who took him to Wayne Manor.
At first, Ace disliked the new Batman, but they eventually warmed to each other. Occasionally, Ace helps the new Batman fight crime.
Official LEGO Description
Rescued by Batman™ and Robin™, Ace the Bat-Hound™ wears a mask to hide his identity as Bruce Wayne’s dog Ace. A trained canine with a keen sense of smell and a fierce sense of loyalty, he wears a tiny receiver in his collar that emits a signal whenever he is needed. Always ready to fight for justice, Ace the Bat-Hound shows immense bravery when tackling villains like the Talon Assassins™ and others.
- Ace's appearance in the game is based off of the Krypto the Superdog cartoon.