The card is a bit clunkily worded, but in essence, it basically splits each player's creatures into two sides of the battlefield (or the "river")

Deck Filters Notion Thief 50%inclusion 39%synergy 1 decks 2 decks Creatures Foulmire Knight 50%inclusion 50%synergy 1 decks 2 decks Brainstealer Dragon 50%inclusion 44%synergy 1 decks 2 decks Keeper of Keys 50%inclusion 50%synergy 1 decks 2 decks The Master, Mesmerist 50%inclusion 49%synergy 1 decks 2 decks Morbid Opportunist 50%inclusion 46%synergy 1 decks 2 decks Phyrexian Metamorph 50%inclusion 40%synergy 1 decks 2 decks Baleful Strix 50%inclusion 26%synergy 1 decks 2 decks Talion's Messenger 50%inclusion 48%synergy 1 decks 2 decks Starscream, Power Hungry 50%inclusion 50%synergy 1 decks 2 decks Sepulchral Primordial 50%inclusion 46%synergy 1 decks 2 decks Agent of Treachery 50%inclusion 47%synergy 1 decks 2 decks Fallen Shinobi 50%inclusion 40%synergy 1 decks 2 decks Hydroelectric Specimen 50%inclusion 42%synergy 1 decks 2 decks Thief of Sanity 50%inclusion 46%synergy 1 decks 2 decks Silent Hallcreeper 50%inclusion 42%synergy 1 decks 2 decks Tinybones, the Pickpocket 50%inclusion 48%synergy 1 decks 2 decks Ashnod, Flesh Mechanist 50%inclusion 50%synergy 1 decks 2 decks Bilious Skulldweller 50%inclusion 49%synergy 1 decks 2 decks Mind Flayer 50%inclusion 45%synergy 1 decks 2 decks Gix, Yawgmoth Praetor 50%inclusion 49%synergy 1 decks 2 decks Intellect Devourer 50%inclusion 47%synergy 1 decks 2 decks Hired Poisoner 50%inclusion 49%synergy 1 decks 2 decks Laboratory Maniac 50%inclusion 46%synergy 1 decks 2 decks Smirking Spelljacker 50%inclusion 49%synergy 1 decks 2 decks Pharika's Chosen 50%inclusion 50%synergy 1 decks 2 decks Dreadwing Scavenger 50%inclusion 49%synergy 1 decks 2 decks Hostage Taker 50%inclusion 46%synergy 1 decks 2 decks Emperor of Bones 50%inclusion 50%synergy 1 decks 2 decks Aura Thief 50%inclusion 50%synergy 1 decks 2 decks Ruthless Ripper 50%inclusion 49%synergy 1 decks 2 decks Nashi, Moon Sage's Scion 50%inclusion 43%synergy 1 decks 2 decks Gonti, Lord of Luxury 50%inclusion 46%synergy 1 decks 2 decks Gonti, Night Minister 50%inclusion 48%synergy 1 decks 2 decks Deadeye Navigator 50%inclusion 47%synergy 1 decks 2 decks Gisa, Glorious Resurrector 50%inclusion 47%synergy 1 decks 2 decks Dauthi Voidwalker 50%inclusion 38%synergy 1 decks 2 decks Thieving Skydiver 50%inclusion 47%synergy 1 decks 2 decks Thieving Amalgam 50%inclusion 49%synergy 1 decks 2 decks Ghostly Pilferer 50%inclusion 47%synergy 1 decks 2 decks Duelist of the Mind 50%inclusion 50%synergy 1 decks 2 decks Kain, Traitorous Dragoon 50%inclusion 50%synergy 1 decks 2 decks Black Cat, Cunning Thief 50%inclusion 48%synergy 1 decks 2 decks Instants Ghostly Flicker 100%inclusion 95%synergy 2 decks 2 decks Blur 50%inclusion 48%synergy 1 decks 2 decks Rapid Hybridization 50%inclusion 39%synergy 1 decks 2 decks Gush 50%inclusion 49%synergy 1 decks 2 decks Shoot the Sheriff 50%inclusion 49%synergy 1 decks 2 decks An Offer You Can't Refuse 50%inclusion 18%synergy 1 decks 2 decks Domineering Will 50%inclusion 49%synergy 1 decks 2 decks Illusionist's Gambit 50%inclusion 48%synergy 1 decks 2 decks Negate 50%inclusion 18%synergy 1 decks 2 decks Consider 50%inclusion 37%synergy 1 decks 2 decks Essence Flux 50%inclusion 46%synergy 1 decks 2 decks Slaughter Pact 50%inclusion 49%synergy 1 decks 2 decks Countersquall 50%inclusion 44%synergy 1 decks 2 decks Reality Shift 50%inclusion 37%synergy 1 decks 2 decks Foil 50%inclusion 49%synergy 1 decks 2 decks Resculpt 50%inclusion 44%synergy 1 decks 2 decks Disallow 50%inclusion 48%synergy 1 decks 2 decks Perplex 50%inclusion 47%synergy 1 decks 2 decks Infernal Grasp 50%inclusion 34%synergy 1 decks 2 decks Siphon Insight 50%inclusion 47%synergy 1 decks 2 decks Lethal Scheme 50%inclusion 48%synergy 1 decks 2 decks Counterspell 50%inclusion -6%synergy 1 decks 2 decks Flatline 50%inclusion 48%synergy 1 decks 2 decks Counterpoint 50%inclusion 49%synergy 1 decks 2 decks Long River's Pull 50%inclusion 48%synergy 1 decks 2 decks Feign Death 50%inclusion 48%synergy 1 decks 2 decks Withering Torment 50%inclusion 34%synergy 1 decks 2 decks Sorceries Come Back Wrong 100%inclusion 99%synergy 2 decks 2 decks Blasphemous Edict 100%inclusion 93%synergy 2 decks 2 decks Diabolic Tutor 50%inclusion 44%synergy 1 decks 2 decks Gitaxian Probe 50%inclusion 45%synergy 1 decks 2 decks Ringsight 50%inclusion 45%synergy 1 decks 2 decks Bribery 50%inclusion 48%synergy 1 decks 2 decks Doomsday 50%inclusion 48%synergy 1 decks 2 decks Blood Money 50%inclusion 48%synergy 1 decks 2 decks Blatant Thievery 50%inclusion 49%synergy 1 decks 2 decks Reanimate 50%inclusion 25%synergy 1 decks 2 decks Inevitable Betrayal 50%inclusion 49%synergy 1 decks 2 decks Rise of the Dark Realms 50%inclusion 40%synergy 1 decks 2 decks Secret of Bloodbending 50%inclusion 50%synergy 1 decks 2 decks Splinter's Technique 50%inclusion 48%synergy 1 decks 2 decks Utility Artifacts Chaos Wand 50%inclusion 49%synergy 1 decks 2 decks Wishclaw Talisman 50%inclusion 46%synergy 1 decks 2 decks Staff of Eden, Vault's Key 50%inclusion 49%synergy 1 decks 2 decks Conjurer's Closet 50%inclusion 47%synergy 1 decks 2 decks The Darkness Crystal 50%inclusion 46%synergy 1 decks 2 decks Chaos Shrine's Black Crystal 50%inclusion 49%synergy 1 decks 2 decks Enchantments Imprisoned in the Moon 50%inclusion 47%synergy 1 decks 2 decks Psychic Impetus 50%inclusion 49%synergy 1 decks 2 decks Steal Enchantment 50%inclusion 49%synergy 1 decks 2 decks Court of Locthwain 50%inclusion 49%synergy 1 decks 2 decks Court of Ambition 50%inclusion 49%synergy 1 decks 2 decks Minion's Return 50%inclusion 50%synergy 1 decks 2 decks Rogue Class 50%inclusion 46%synergy 1 decks 2 decks Kaya's Ghostform 50%inclusion 47%synergy 1 decks 2 decks Fealty to the Realm 50%inclusion 50%synergy 1 decks 2 decks Animate Dead 50%inclusion 39%synergy 1 decks 2 decks Public Enemy 50%inclusion 50%synergy 1 decks 2 decks Curse of Verbosity 50%inclusion 49%synergy 1 decks 2 decks Black Market Connections 50%inclusion 39%synergy 1 decks 2 decks Mind's Dilation 50%inclusion 48%synergy 1 decks 2 decks Cunning Rhetoric 50%inclusion 48%synergy 1 decks 2 decks Propaganda 50%inclusion 32%synergy 1 decks 2 decks Parasitic Impetus 50%inclusion 49%synergy 1 decks 2 decks Eye of Nidhogg 50%inclusion 49%synergy 1 decks 2 decks Sothera, the Supervoid 50%inclusion 49%synergy 1 decks 2 decks Planeswalkers Ashiok, Sculptor of Fears 50%inclusion 49%synergy 1 decks 2 decks Utility Lands Bojuka Bog 50%inclusion 11%synergy 1 decks 2 decks Mystic Sanctuary 50%inclusion 33%synergy 1 decks 2 decks Witch's Cottage 50%inclusion 47%synergy 1 decks 2 decks Castle Locthwain 50%inclusion 47%synergy 1 decks 2 decks Reliquary Tower 50%inclusion 14%synergy 1 decks 2 decks Rogue's Passage 50%inclusion 23%synergy 1 decks 2 decks Agna Qel'a 50%inclusion 48%synergy 1 decks 2 decks Realm of Koh 50%inclusion 49%synergy 1 decks 2 decks Mana Artifacts Arcane Signet 100%inclusion 16%synergy 2 decks 2 decks Talisman of Dominance 100%inclusion 42%synergy 2 decks 2 decks Sol Ring 100%inclusion 12%synergy 2 decks 2 decks Everflowing Chalice 50%inclusion 44%synergy 1 decks 2 decks Dimir Signet 50%inclusion -8%synergy 1 decks 2 decks Fellwar Stone 50%inclusion 19%synergy 1 decks 2 decks Thought Vessel 50%inclusion 19%synergy 1 decks 2 decks Mind Stone 50%inclusion 22%synergy 1 decks 2 decks Prismatic Lens 50%inclusion 48%synergy 1 decks 2 decks Lands Tainted Isle 100%inclusion 56%synergy 2 decks 2 decks Command Tower 100%inclusion 13%synergy 2 decks 2 decks Swamp 100%inclusion 3%synergy 2 decks 2 decks Drowned Catacomb 100%inclusion 45%synergy 2 decks 2 decks Underground River 100%inclusion 59%synergy 2 decks 2 decks River of Tears 100%inclusion 90%synergy 2 decks 2 decks Island 100%inclusion 3%synergy 2 decks 2 decks Sunken Hollow 100%inclusion 35%synergy 2 decks 2 decks Choked Estuary 100%inclusion 53%synergy 2 decks 2 decks Dimir Aqueduct 50%inclusion 13%synergy 1 decks 2 decks Darkwater Catacombs 50%inclusion 11%synergy 1 decks 2 decks Hydroelectric Specimen 50%inclusion 42%synergy 1 decks 2 decks Shipwreck Marsh 50%inclusion 10%synergy 1 decks 2 decks Path of Ancestry 50%inclusion 23%synergy 1 decks 2 decks Sunken Ruins 50%inclusion 33%synergy 1 decks 2 decks

"No matter what happens, if we stick together, we can get past it
The upcoming Universes Beyond set references a range of Fallout games, but Vault 21 is a slice of Fallout: New Vegas
If youre playing Pioneer Masters Limited, things will be a little different
You can use this flexible construct as a beat stick that grows, as a card draw engine if you can sacrifice it, or even as a wincon should you draw your entire deck