Stampede

An instant-speed team pump with a deliberately narrow brief: it adds power, not toughness, and only for creatures already attacking. The trample grant is what makes the +1/+0 matter, turning a board of small attackers into damage that ignores the chump-block math an opponent was counting on. Because it resolves at instant speed, it lives inside the attack step, after blocks are declared, when the defender has committed to a plan and can no longer adjust the count. Withholding toughness is the honest part of the deal: this closes games rather than saving creatures, so it asks you to be ahead on bodies before you cast it instead of rescuing a doomed trade. As a green mass-trample effect it descends from Overrun, but at one power per creature it favors the swarm over the alpha strike, ending a game two turns early once the board has gone wide rather than punching one fattie through. The trample is the lever; the power bump is the multiplier riding on it.