Dungeon Geists

Dungeon Geists is a Commander card through and through — the tap-lock effect compounds over multiple turns in longer games, and blink engines like Brago, King Eternal or Teleportation Circle turn a single enters-the-battlefield trigger into a lock on two, three, or more threats. In Modern and Legacy the competition at four mana is brutal, and a 3/3 that doesn't immediately end the game is a non-starter in those formats. Pioneer has the same problem — creature-based tap effects don't survive in environments where removal is cheap and fast. Dungeon Geists is a Commander-only card in practice, and even there it's best in a deck built around abusing enters-the-battlefield triggers rather than as a generic blue inclusion.