Cards like Mycosynth Lattice or Trinisphere push Karn from irritating to game-ending, and the fact that this happens without attacking explains why he ranks among good planeswalkers, arguably one of the best to ever get printed for artifact-heavy metas
Finally, there's Y'shtola
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Armadillo Cloak already very good, but it is borderline broken in the right shell in Eternal Masters
Peace Offering While bribing your opponents is a reliable way to keep them off your back for a couple of turns, group hug decks can be a real slog, especially late-game