Tsabo's Assassin

What this assassin reads isn't the creature in front of it but the whole battlefield's color census: tap it and it polls every permanent for the most-represented color, then fires only on a creature that shares it. Crucially, colorless permanents don't vote, so the relevant count is the colored permanents on the board: enchantments, colored artifacts, planeswalkers, colored lands, and most of all creatures. In a table heavy on one color, the assassin becomes a precise answer against exactly that color; spread the colors evenly and ties widen its reach, since a color tied for most-common counts too. The ability carries no timing clause, so the removal fires at instant speed, and the no-regeneration rider closes the door on anything that would otherwise crawl back. The cleverness is also the catch: the killable color recalculates with every shift in the board state, so the same 1/1 can tighten or loosen its threat range turn to turn without anyone touching it. And because it's an activated ability you choose to point, a board where your own color dominates simply narrows what the assassin can legally kill on opposing creatures; you never have to fire it at your own. It belongs to the strain of early color-mattering design that treated the dominant color on the battlefield as a readable resource. Most of those cards handed out upside for color counting; this one inverts the idea into a kill condition, asking its controller to track the table's color math rather than the spell in hand.