They mutate into the creature on top plus all abilities from under it.) Whenever this creature mutates, return target permanent card from your graveyard to your hand
Im giving this a C
It becomes a 0/0 Bird creature with flying in addition to its other types
As for the multiple cards you have to discard, consider this opener: Turn 2: Jace, Vryns Prodigy Turn 3: Discard Stitchwing Skaab, followed by discarding Geralfs Masterpiece and Prized Amalgam
Since you have ways to give artifact creatures myriad, this gives you three token copies of them which can spiral into taking multiple extra turns
There and Back Again Look, Im not going to leave off the card that says Create fourteen Treasure tokens. There and Back Again isnt that special, and the Smaug tokens a little disappointing, but the overall package on this saga is fun and flavorful, and it gives players a dream worth living for if they can slay the dragon