The key card is present but its support is thin.
Prioritize useful support such as Shinra Reinforcements or Vanille, Cheerful l'Cie.
Reinforcements mills and stabilizes; Vanille can recover a useful permanent from the growing graveyard. Keep six permanent cards there before Exdeath’s end-step check if transforming is the goal.
Your deck already enables the plan but is losing the early turns.
Take a castable early creature or efficient answer before a second expensive payoff.
Instants and sorceries do not count for Exdeath’s permanent-card threshold. Returning permanent cards to hand can postpone the transformation, so choose the resource that matters now.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.