Make sure you can sacrifice or kill the Zombie Army token each turn so Dreadhorde Invasion makes a new one instead of adding a counter to an existing one
Its far easier to walk back creating a token than drawing a card off of Rhystic Study, afterall
It fits beautifully into grindy or value-based merfolk builds, especially with cards like Deeproot Waters or Deeproot Pilgrimage
1 The One Ring - 1/1 $2,000,000 A unique card in every sense, this one-of-one variant of The One Ring from Tales From Middle-Earth is in Post Malone's possession, who famously purchased it for $2,000,000 when it was discovered in a pack in Toronto
Sacrifice Elves when they die naturally to turn them into graveyard fuel
Cards like Soul Warden, Ajani's Welcome, Kor Celebrant, and Impassioned Orator can turn the smallest token into a big buff for your creatures, while it can combo with stuff like Spike Feeder, Fathom Mage, and Horizon Chimera for infinite lifegain