Soul Snare

A deterrent that works while it sits face-up. The exile only fires against a creature already attacking you or a planeswalker you control, which means the enchantment earns its keep before it is ever activated: it taxes the decision to swing rather than the board. That conditional is the whole bargain. Where Swords to Plowshares and Path to Exile answer any creature at any time on your terms for a single mana, this one waits for the opponent to commit to combat and asks for two white mana total (one to cast, one to crack it), trading both speed and flexibility for the patience of a permanent that stays a threat turn after turn. The activation is instant-speed, so it slots into the window after attackers are declared but before damage, letting one white mana erase the largest creature in a swing. Exile is the clean part of the answer: no death triggers, no regeneration, no return from the graveyard, the card simply gone. The sacrifice clause is what keeps it from becoming a recurring fog: one removal, then it leaves the battlefield, so the deterrence has a hard ceiling the attacker can play around once they know the trade. It is a low-rarity sentinel built for grindy multiplayer tables, where a piece of visible interaction discourages attacks more reliably than any hidden trick, and where the planeswalker clause guards the part of your board that needs a turn cycle to pay off.