Enduring Vitality Go wide strategies can benefit from a way to make their Creatures tap for mana and Enduring Vitality offers some more redundancy for that effect
It is provided to players (at no additional cost) who purchase a full booster box, while supplies last and only to customers that pick up their booster box in-store
"Magic: The Gathering Comprehensive Rules" (PDF)
Its controller creates a token thats a copy of it, except its not legendary and its an artifact in addition to its other types
This doesnt double as a finisher itself the way that Finale of Devastation does, except that casting this for x=8 and finding Craterhoof Behemoth is usually close enough
Of course, this means you need a character on board that can initiate the challenge before Maid Marian gets value, but there are 11 4-cost characters that all have decent Strength values, so it isn't hard to get something down the previous turn that can take the Challenge