Backup is another +1/+1 counter mechanic at its foundation, so it naturally fits with the counter support that already exists
Treasure Booster Set - One Piece Promotion Cards One Piece - Collectr
Merfolk is a good one, Wizards can go mono blue (Patron Wizard), loads of combo decks and artifact ramp decks are also fine to be mono blue for
The guides in the box show you how and help you sharpen this skill for an even faster win
Each pack contains 15 cards and 1 foil double-sided token, with 1 foil alternate frame rare/mythic (Expedition, showcase, borderless, or extended art), 1 foil rare or mythic, 1 non-foil borderless or showcase rare or mythic, 1 non-foil extended art rare or mythic, 1 foil showcase common/uncommon, 2 non-foil showcase commons/uncommons, 2 foil uncommons, 5 foil commons, and 1 foil full art basic land.
Section 31 Summary Input: One playing of Garza's Assassin Output: Lots of reuse of Southern Paladin Layer count: For each Bloodbond March, for each Clash of Realities on a new Mimic Vat, for each Guilty Conscience on Mimic Vat, for each Rite of Passage putting counters on Mimic Vat, for each Doubling Season on the Rite of Passage counters added to Mimic Vat, for each Rings of Brighthearth on Sinking Feeling's ability while it's attached to Mimic Vat, for each Rings of Brighthearth on Mimic Vat's ability, for each Doubling Season on the tokens created by Mimic Vat, for each Rings of Brighthearth on Garza's Assassin's ability, for each Grip of Chaos, for each Psychic Battle...11
