Serpent's Gift

Granting deathtouch at instant speed turns a combat step into an information trap, and that inversion is the whole strategic point. The keyword is usually printed onto a body, where its presence is static and telegraphed: opponents see the deathtouch and decline the trade. Stapling it to an instant flips that calculus. You hold up the mana, let the opponent commit to a block or an attack against a creature that looks safe to fight, and only then make the trade lethal once the chump has already chosen wrong. A single mana dork can suddenly eat a dragon. Because deathtouch governs any damage the target deals, not just combat damage, the trick also amplifies a fight spell, a bite effect, or even a one-power pinger into a kill: every point of power the creature deals to another becomes a full destroy. That is the tension green has always wrestled with, a color flush with fat bodies but short on reliable spot removal; deathtouch is its sanctioned way to make raw power do the work of removal. What balances the spell is that it has to attach to a creature already poised to deal damage to something. With no legal target it is dead in hand, and on a creature with no fight or combat lined up, it does nothing; it lives and dies as a trick you commit to the board in front of you, never an answer you can point from a position with no pieces of your own.