This card has changed much since it's debut, with a very different each time. It started out with being able to reset the cooldown of an ally monster, making it a single target, all class version of Final Charge. Beta 7.1 changed that to killing the monster with the higest ATK, which included allies and would be random if multiple cards had the highest ATK.
Beta 7.3 changed it again to it's current state, which makes it so that when you have this on the board, it get's +1 HP when you summon another monster, and +1 ATK when your opponent summons a monster. This can be useful when you're using and/or facing a rush deck, as those kind of decks focus on placing as many cards as possible. Those kind of decks are most common with Bravery and Integrity.