Heroic Charge

The kicker cost is the whole design conceit here: a white anthem trick that stays castable in a mono-white shell but reaches into red for the finisher clause. Base mode is a familiar team pump, +2/+1 across the board at instant speed, meant to blow out a block step or push a wide board through a stalled ground. Pay the extra and every creature gains trample, which converts the pump from a combat trick into a lethality tool: against a defensive wall, +2 power that spills over is worth far more than +2 power that gets chump-blocked away. The construction rewards a deck already leaning Boros without punishing one that never draws the red: the kicker is upside, not a tax. What tempers it is the four-mana floor and the double-white pip; a team-wide +2/+1 at that cost only pays off on a developed board, so this is a spell that wants to be the last card you cast rather than the first, cast into an attack that is already threatening. The trample rider is the cleanest expression of what red brings to a white aggro plan: not more bodies, but a way to make the bodies you already have refuse to be soaked up.