The term "defending player" in the myriad rules (or any other ability of an attacking creature) refers to the player the creature with myriad was attacking, the controller of the planeswalker it was attacking, or the protector of the battle it was attacking at the time the ability resolves
With Amulet of Vigor in play and enough lands on the battlefield, casting Scapeshift to fetch two Lotus Fields, Simic Growth Chamber, Tolaria West, and Shifting Woodland unlocks a chain reaction: the bounce land returns Tolaria West, which transmutes for Summoner's Pact, which finds Aftermath Analyst
It is good because it is free not because 1/1s are good
On the Trail and Summer Bloom let you convert your cards to victory faster than your opponents, at least so you hope, and then you pack all the protection spells you can cram into the 99
Renewed Leader Cards : King in purple-black with enhanced effects
WOTC pivoted the general exploration story to a race to find the resource cosmium