Keep Out

In Commander, Keep Out pulls its weight as a one-mana fog against the whole table, which is where the math flips in its favor — a single card neutralizing three opponents' combat steps is the kind of asymmetry white defensive decks are built to exploit. Competitive formats are less forgiving: Modern and Legacy have access to faster win conditions and more resilient threat density, so a one-turn fog rarely does enough work outside of very specific control or combo-protection shells. In Pauper and Pioneer the card is legal but sees minimal play, since dedicated combat-based aggro in those formats often closes games before a single defensive instant changes the calculus. Keep Out is a Commander card through and through.