Subdue

A Fog spell that pretends to be a buff. The damage prevention is the load-bearing half: for one green mana at instant speed, you blank an attacker or blocker's combat damage entirely, the same kind of trick a Holy Day or a Moment's Peace pulls, only laser-targeted. The +0/+X rider is the design's strange flourish, scaling toughness by the creature's mana value so the prevented attacker also becomes harder to kill in the same combat step it just whiffed in. That second clause is the tell that this is a Legends-era card: the modern instinct would be to leave it as clean prevention, but early design routinely stapled odd, mechanically tangled secondary effects to single-color instants to justify the rate. The result is a green spell that wants to protect your own creature from a damage-based answer (cast on a creature with mana value four, the toughness bump alone can lift it out of Lightning Bolt range) at least as often as it wants to neutralize someone else's attacker. That dual-purpose framing was rare in green, a color whose combat tricks usually committed to one side of the table or the other. Subdue's value is mostly historical now (the rate on pure prevention has been outrun and the toughness boost is too situational to anchor a card), but as a snapshot of how 1994 green thought about combat math, it is unusually legible.