Some of the most useful ones are: Tamiyo's Safekeeping, Veil of Summer, Shardmage's Rescue, Surge of Salvation, and Snakeskin Veil
As an added bonus for this attack, mill, play a land sequence, whenever one or more cards leave your graveyard, youre able to spawn a 2/2 black Zombie Druid creature token
For five converted mana, you get a 5/5 creature with a host of abilities
For example, if you control a creature and your opponent targets it with a Doom Blade, you could sacrifice it to an outlet like Carrion Feeder after Doom Blade hits the stack but before it resolves
Mewtwo ex works in a similar way as Charizard ex, though as a basic Pokmon itself, players will often put it directly into the active Pokmon slot
This discounts all your creatures, all while becoming a terrifying threat once it starts mutating frequently