Dwarven Ruins

Dwarven Ruins sees essentially no competitive play in Legacy or Vintage, where the tempo loss of entering tapped is punishing and true rituals like Rite of Flame exist. In Commander, the case is marginally stronger — singleton rules mean some mono-red builds hunting every scrap of red mana redundancy will consider it — but the sacrifice clause means it contributes nothing past the turn you crack it, leaving you down a land for the rest of the game. Oathbreaker shares Commander's singleton constraint but the faster pace makes the enter-tapped drawback worse, not better. Across every legal format, Dwarven Ruins is a fringe card that only earns a slot when the deck genuinely needs a fifth or sixth copy of a burst-mana effect and has nowhere else to turn.