Eidolon of Obstruction

In Commander, Eidolon of Obstruction punishes tables running planeswalker-heavy strategies, and in four-player games the cumulative tax across multiple opponents adds up fast — it earns its slot in white stax or hate-bear shells built around Thalia, Guardian of Thraben or similar taxing commanders. In Modern and Pioneer, it sees fringe sideboard play against planeswalker-dense midrange decks where slowing down Teferi or Liliana by a turn can matter, though dedicated removal usually answers the Eidolon before it accumulates value. Legacy and Vintage have enough fast mana and cantrips to make a 2/1 body feel fragile, so it rarely sees maindeck play there. Oathbreaker is where Eidolon of Obstruction arguably has the highest ceiling — since the signature spell and oathbreaker both use loyalty-style activations, the tax hits the core engine of the format directly.