Any Battle Damage your opponent takes from battles involving this card becomes 0. Once per turn: You can target 1 Effect Monster in your Graveyard; banish that target, then, until the End Phase, this card’s name and ATK become that monster’s name and ATK, and it gains that monster’s effects. You must control this face-up card to activate and to resolve this effect.
Phantom of Chaos is in a unique position this format. There are a TON of great cards to be removed (I thought of one right now), meaning this card is very splashable.
As a dark monster, it provides the necessary buzz for a Chaos Sorcerer or a Black Luster Soldier – Envoy of the Beginning. It is searchable with 0 attack by Sangan and as a level 4 monster by Summoner Monk. It even makes great Xyz material into Roach, Utopia, or Zenmeister.
Some obvious uses of the card have already been stated. Banish BLS and attack twice/banish an opponent’s mosnter. Banish Summoner Monk and ditch a spell to search for a level 4.
It pairs with Lightsworns, allowing you to pirate the effects of cards like Lyla, Lumina, or even Judgment Dragon. Since Phantom of Chaos takes the name of the monster it removes, perhaps it could even be used as the tribute to bring out Celestia.
Light of Redemption allows you to add any removed from play light monster, like Judgment Dragon for example, to your hand for 800 Life Points. One could potentially get an incredible amount of mileage from any powerful light monster whose effect activates on the field. Escape from the Different Dimension and Escape from the Dark Dimension combo well with PoC to bring your removed dark monsters to the field, and you can always rely on Dark Eruption (and to a lesser extent Recurring Nightmare) to add PoCback to your hand.
Here is just a brief example of monsters that Phantom of Chaos can loot for great outcomes:
Dark Armed Dragon
Black Luster Soldier – Envoy of the Beginning
Fortune Lady Dark
Brionac, Dragon of the Ice Barrier