Shadow Sliver

Slivers are an additive tribe: every keyword grant since the archetype debuted has stacked another piece of upside onto a shared board, never charged anything for it. This one breaks that pattern by handing the whole team an evasion ability that costs something real. Shadow pulls a creature off the standard combat plane entirely, into a separate layer where it can interact only with other shadow creatures, and granting it tribe-wide turns the swarm untouchable in one direction while sealing it off in the other. Your Slivers stop being blocked, but they also stop blocking the opponent's ground creatures, so the moment this resolves your defensive wall ceases to exist. That makes it a commitment to racing rather than grinding: it asks a board that is already ahead and wants the game to end before the missing blockers matter. Where every lord-style Sliver adds reach without subtraction, this one trades the tribe's entire defense for an offense nobody on the ground can answer. For a creature type whose identity is pure accumulation, a keyword that takes a tool away while it hands one over is the genuine design oddity in the library.