needs Japanese size sleeves
Cerberus (0368 - Borderless) Final Fantasy Variants $2.29 Summon: Brynhildr (0366 - Borderless) Final Fantasy Variants $1.99 Excalibur II (0352 - Borderless) Final Fantasy Variants $1.79 Stiltzkin, Moogle Merchant (0327 - Borderless) Final Fantasy Variants $2.99 Gilgamesh, Master-at-Arms (0338 - Borderless) Final Fantasy Variants $0.99 Tellah, Great Sage (0349 - Borderless) Final Fantasy Variants $1.49 Sin, Spira's Punishment (0348 - Borderless) Final Fantasy Variants 0 results found

Of those, here are the ones probably relevant for a deck like this: Elvish Archdruid (large mana production) Greatbow Doyen (unique damage dealing) Joraga Warcaller (build-your-own buffs) Lord of Atlantis and Master of the Pearl Trident (Islandwalk) Lord of the Unreal (mass Hexproof) Merfolk Sovereign (unblockable) Myr Galvanizer (mass untap) Scion of Oona (mass Shroud) Seshiro the Anointed (Coastal Piracy effect) Timber Protector (mass Indestructible) Vodalian Hexcatcher (countering, low relevance in Commander) Some of these are pretty decent, particularly the ones with sweeping protection like Lord of the Unreal and Timber Protector
Theres not much more to say here other than that if you like to play these kinds of combos, consider adding Vivien to your deck
Maulfist Doorbuster: [Category 2] ETB yield is 2 Energy for 4 mana, then you can spend 1 Energy to cause a creature not to block