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
There's a lot of staples for Counters decks here, like Inspiring Call, Inexorable Tide, Hardened Scales, and it's the first time we've seen Damning Verdict reprinted, one of the best cards for a Counters deck as a one-sided wipe and it was quite expensive for that reason
$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
He even works well on his own if you build him on his own, giving you incentive to play lots of tokens and get increasing value out of them
You've got it
Remarkable Gentleman is used to Sing, Savvy Opportunist is another decent Evasive character, and Agent Provocateur adds recursion