Dauntless River Marshal

In Commander, Dauntless River Marshal slots cleanly into Azorius or mono-blue control builds that already run a heavy Island count — the tap ability doubles as a threat deterrent and a combat trick, and the stat growth gives it late-game relevance most two-drops lack. Outside blue-heavy shells it does almost nothing, so it earns zero slots in three- or four-color decks where Islands thin out. In Legacy, Modern, and Pioneer it's too slow and too conditional; format staples at the same cost do more without the Island clause. Vintage has the same problem at a higher power ceiling. Oathbreaker mirrors the Commander calculus — run it if your signature spell is blue and your mana base supports it.