Stronghold Furnace

Damage doubling as an ambient effect, applied to every source at once, is the kind of blunt symmetry that only makes sense on a card no one has to pay for. There is no mana cost, no color, no summoning restriction: with this in the pile, every point of damage anyone deals lands as two, from combat to burn spells to the plane's own chaos trigger firing back into the multiplier. That symmetry is the whole tension. Doubling helps whoever is dealing the most damage this turn, which usually means the aggressor, but it does not choose sides, so a defended attack answered with a doubled block goes just as badly. The chaos trigger adds a small self-referential wrinkle: it pings for one, which the effect then reads as two, a source doubling its own output the instant it resolves. As a piece of the oversized-plane format, it belongs to the wing of that pool designed to warp the math of every game happening around it rather than to reward the planeswalking player specifically. It is a global multiplier with no owner, which makes it read less like a strategy and more like a hazard: the board is now twice as lethal for everyone, and the only question is who was closest to winning when the die came up chaos.