There's nothing more terrifying in a game than seeing a boss mutate or evolve into a brand-new form. Most of the time, this will result in the enemy gaining all of their HP back, but on some occasions, they can even achieve a few new buffs and abilities to make the fight even more challenging. Inserting a multi-phase boss into a game is always a gamble, since it can cause a fight to go on for very long and will provide a true test of the player's determination and patience.