Reverent Mantra

Choose the attacker's color and your whole board, plus theirs, walks through that color untouched until end of turn. As a defensive play that reads as a Fog with teeth: it not only blanks combat damage of the named color to your blockers but also voids targeted removal and aura attachments in it. What separates this from an ordinary protection trick is the alternative cost: exile a white card from hand and you cast it for nothing, leaving every land untapped to develop, hold up a counterspell, or rebuild the same turn you survive an alpha strike. That belongs to a small early-era cycle of color-keyed spells castable by exiling a card of the matching color, a design that trades card economy (two cards spent to net one effect) for the ability to operate at an effective cost of zero. For a reactive instant, that has always been the axis that matters: not the printed price, but whether you can leave it up while spending your turn elsewhere. The catch is the single-color lock. The grant only stops one chosen color, so it shines against a focused mono-colored assault and falters against a board spread across colors. Against the right attacker, though, it erases an entire turn for the price of a card you were never going to cast.