Any cards with scavenge that get put into the graveyard become spells of sorts that can add +1/+1 counter boosts to creatures on the battlefield
So instead, Ill add to this scenario that you dont have the Mewtwo on bench, and need to draw it from your deck
We have already seen creatures, enchantments and one notable planeswalker printed on the opposite side of teased battle cards, including the Marchesa of the niche plane of Fiora or a towering apex predator from Ikoria - the designers said on the stream that theyre digging deep for planar callbacks as well as revisiting recent favourites in March of the Machine
Obviously, Black Lotus is the headliner here, providing a huge burst of ramp, but the other options are valuable in their own right
Grave Upheaval then is not just a recursion spell for the best creature in all graveyards, but a great spell that can keep your land drops on curve in a pinch