User Summary Altered Beast: Guardian of the Realms is a Game Boy Advance exclusive and a sequel to Sega's classic Altered Beast. The game borrows its feel from Castlevania titles on the Game Boy Advance, but preserves the storytelling method of the original Altered Beast. Once again, Zeus summons you from your grave to combat the forces of evil, which you do with several weapons and with the ability to morph into a variety of powerful beasts.