The best part of this ability is that if that Dragon is legendary, the token version is nonlegendary
Judith, the Scourge Diva will have some fun with this card, shes always a fan of chaos and carnage, especially at the cost of her own creatures
There is a lot of competition when it comes to Zombie-based decks, but Eternal Might is Esper (white/blue/black), an untraditional color trio for Zombies, allowing it to play unique white enchantments for extra boosts
Beyond that, you have the usual suspects when it comes to making a tight EDH mana base: Theres fetches and shocks and duals, with the surveil lands feeling better than ever in a deck with reanimation spells (though Id play them regardless)
Whichever you choose, you'll still be getting a 10 mana 7/7 (plus a number of +1/+1 counters equal to the highest mana value of cards in exile) with annihilator x equal to the number of counters and ward that exiles half of your opponent's library