Null Elemental Blast

The lineage runs straight back to the Blast cycle: Red Elemental Blast and its blue mirror have been color-hosers since the earliest days, one mana to answer a spell or permanent of the enemy color. What changes here is the axis of hatred. Instead of naming a color, this hoses the fact of being more than one: any spell or permanent painted in two or more colors is a legal target, regardless of which colors. That reframing is sharper than it looks, because the decks most punished by it (multicolor goodstuff, gold-heavy midrange, commanders that lean on splashy multicolored payoffs) are exactly the strategies that treat their color count as a strength rather than a liability. The masterstroke is that the answer itself takes no side in the color wars: every prior Blast demanded you play the answering color, while this one asks only that your manabase can produce true colorless mana, so any deck built to generate can pack it without committing to a color allegiance. It is modal in the classic Blast shape (counter on the stack, destroy on the battlefield), so it covers both the window before a threat resolves and the aftermath if it already did. As a piece of sideboard hatred it is almost pure upside against the field it targets and a dead card against monocolor, which is precisely the honest tradeoff a hoser should carry.