The X is going to have to be large to be significant, especially since proliferation isnt the best option in this +1/+1 counters deck
Notably, the legendary creatures are eternal legal, meaning players can use them in Legacy, Vintage, and Commander
Locus of Rage makes 5/5 Elementals and Lightning Bolts when it or an Elemental die
Humans and machines working together can be fearsome indeed! Arcum Dagsson Illustrated by Greg Simanson Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
Ugin, the Spirit Dragon While I have balked a lot at seven mana Wrath effects this 8 mana one is pretty potent
You wont always want to sacrifice a land to do that either, but you should definitely consider this in decks that care about lands going to the graveyard