Bruiser is the whale in HALO whose power is size alteration.
Bruiser was born as Benjamin Bailey. His parents are an as-yet-unnamed pair of whales of mismatched species. To aid conception, Ben's mother took a serum which would insure genetic compatibility. As a result, Ben was born mutated. He is not the only mutant whale, and in fact has spent the bulk of his life in the Atlantis colony of mutant whales.
Bruiser's power is size alteration. Bruiser is also able to change his mass by unknown means. The number of particles in his body remains constant, and even the particles themselves appear to change size, allowing him to shrink even smaller than a quark. His power can be channeled so that it includes his clothing and tools, and has even been channeled throughout the shrinking ship Supernova.
The catch to these powers is that they are linked to Ben's emotions. In order to control his powers, Ben must exert control over his own emotional state. He learned to do this with reasonable reliability during his stay with Dark Avenger Nine. This may have also been influenced by the proximity of Darkmask.
Naturally, Bruiser also has all the powers of a whale, including super-strength and endurance, sonar, aquatic freedom and a voice which carries for hundreds of miles. He also has the weakness of needing frequent rehydration.
Bruiser is half blue whale, half sperm whale. He has the box-shaped skull of a sperm whale, but the jaw and baleen of a blue whale, as well as the flanges on his flippers. He also possesses an enormous chin, his most striking feature. Even when his power is not active, Ben is large, even for a whale. His size is only surpassed by the largest mutants, such as Abraxas. Bruiser's uniform has seen several variations, but the color scheme tends to stay with red and blue. Unlike many of the citizens of Atlantis, Ben prefers to remain clothed except when asleep.
Bruiser has a strong desire to do good and make the world a better place. His biggest frustration is that he is never able to do enough.
For many years, Ben held a grudge against his parents because of his mutation. Only recently has he sought to reconcile with them.
Ben is known as "Tiny" in Atlantis because of his chronic shrinking.