Rebel decks often just dropped down Lin Sivvi and then never cast another spell the entire game, instead building up their forces and mana base turn after turn
With so many different multicolour lands available to us in Pioneer, the mana in three-colour decks will already be quite good, which eats into at least a bit of the appeal of playing Attune with Aether
Skyshroud Claim is a four mana green sorcery that searches for two Forests in your library and puts them into play untapped
The overall land distribution remains the same except for the removal of the rare Islands (which leaves Islands being slightly short printed, although replacing an uncommon with a rare in the starters slightly mitigates this)
Red Great artwork, mediocre sacrifice fodder, and thats about it
You can always target your own creature if it's about to die anyway, hopefully one with a good enters-the-battlefield effect