If a spell with rebound that you cast from your hand doesn't resolve for any reason, including being countered, that spell won't resolve and none of its effects will happen, including rebound
Maria Zafrilla and Beatrice Blue helped us with this for Archazias Island
As for Shadow itself, card draw is nice but the real draw here is the fact you can repeatedly drain each opponent of life whenever you trigger this ability
9 Tamatoa, Happy as a Clam Item Recursion Tamatoa is a fan-favorite character from the Moana series
But when you tack on milling synergies in its first chapter, returning all lands from your graveyard to the battlefield in the second chapter and another target creature getting +X/+X equal to the number of lands you control in the final chapter, youve got the makings of a top-flight game-finisher and yet another example of Summons being playgrounds for the Timmys/Tammys of the world (like me)
Then if Cloud has power 7 or greater, create two Treasure tokens