Bruce was normal and so was his parents until he was taken away from them at the age of 6 by Desdemona. Desdemona experimented on him with other being's blood being injected into him and putting a curse on him. The curse was what saved him. Bruce changed into his beast form and escaped from Desdemona when he was 17. The beast had instincts that took it to Springville where Bruce turned back into his normal self. He was only there for a few days before a wormhole opend, him falling into it and being transported to 2017.
Shapeshifting: Bruce can turn into a monster sometimes at will. The monster is much stronger, has better senses, faster and bigger than Bruce and it is also very animal like.
Frost Giant Abilities: Thanks to Desdemona, Bruce is part-giant and has much more strength than a normal human, can cast illusions and control the cold.
Legacy Abilities: Having a child of Ares blood in him from Desdemona, Bruce can control any weapon and learn to use any weapon easily.