The summons used in all the decks, but most prominent in the Final Fantasy 10-based Counter Blitz, are reminiscent of the Sagas of Kamigawa: Neon Dynasty, except that they start as enchantment creatures and are sacrificed after three turns
$25 Upgrade +1/+1 Counters is a very deep archetype so there's more sweet upgrade options that I could ever hope to cover, but I selected some of my favorites: for protection I've added Bulwark Ox and Mutational Advantage, a bunch of proliferates with Metastatic Evangel and Dreamtide Whale being the two best, ramp got a massive upgrade with Astral Cornucopia / Kami of Whispered Hopes / Purestrain Genestealer / Summon: Fenrir, and so on
Spell Snare is also great against decks with Snapcaster Mage, Affinity of all types, Storm, and a slew of other decks that lay threats in the early game
Zask, Skittering Swarmlord Zask, Skittering Swarmlord leans hard onto insect creatures to fuel its graveyard strategy
Now that Universes Beyond sets are Standard-legal, and have even lost the distinctive card borders that separated them from regular cards, Universes Beyond sets are also released on MTG Arena (and MTG Online)