Yuna, Hope of Spira Series: Final Fantasy X Spoiler Level: High A pretty straightforward effect for the token summoner of FF10
If a spell with rebound that you cast from your hand doesn't resolve for any reason, including being countered, the spell will be put into its owner's graveyard and you won't get to cast it again on your next turn
The goal of this deck is to utilize the hand discard + refill of Sauron's last ability to enable a powerful Grixis Reanimator style of deck, ramping out Sauron, discarding cards we want in the graveyard while drawing, and then cheating out haymakers from the graveyard for more value
That alone is quite strong, but since it distributes a "Grave Pact" effect to other deathtouch creatures, creature combat becomes quite hopeless
Hapatra, Vizier of Poisons Hapatra, Vizier of Poisons is all about those -1/-1 counters, and its ability to create tokens and other synergies with them lands it pretty high
Celestine does require you to gain life before you can start bringing creatures back, with so many ways to efficiently gain life in Commander this isnt a problem at all