Mortal's Resolve

The two-mana protection trick lives or dies by what it answers, and this one answers nearly everything at once: a single spot-removal spell, a combat trade you want to win for free, a board wipe you saw coming. Indestructible until end of turn is the broadest shield green could ask for at this price, neutralizing damage and "destroy" effects alike, and the +1/+1 keeps it from rotting as a pure reactive blank when there is nothing to protect against. The cost it pays for that breadth is the cost every protection spell pays: it does nothing against exile, against bounce, against -X/-X, against sacrifice edicts. The shield is wide but not deep, which puts the burden on reading what kind of removal your opponent is holding before you spend it. Green has cycled through this design many times at slightly different rates and riders, and the through-line is always the tension between protecting your investment and holding up reactive mana that may sour in hand if the threat never comes. As a body-pumping instant it sidesteps the sorcery-speed window most green effects sit in, and that flexibility is where its value concentrates: you can hold it, threaten it, and let the bluff do work even on the turns you never cast it.