Savanti Romero, Time's Exile

Commander is the only format where Savanti Romero, Time's Exile does anything meaningful — the design is explicitly parasitic on the command zone rule, so it reads as a blank in Legacy, Modern, Pioneer, and Standard where commanders don't exist. In EDH, the play pattern is surgical: you slam it to neutralize a problematic commander and force your opponent to recast from the command zone at escalating costs, but it only targets one player and has no secondary function once that threat is handled. Oathbreaker is the one other format where the card has teeth, since planeswalker commanders are equally susceptible to the same lock.