Pyromancer's Gauntlet

A static damage-amplifier built around a deliberately narrow replacement effect: it only touches red instants, sorceries, and planeswalkers, and only when they would deal damage to a permanent or player. That restriction is the whole design. Rather than pump every damage source you control, it asks you to commit to a deck whose win condition runs entirely through red spell damage, and it pays a flat +2 per instance rather than a multiplier, so the reward scales with how many separate damage events you can chain rather than how big any one of them is. Because it rewrites the damage as a replacement, the bonus applies per event: a single burn spell that hits five separate targets gains two on each, and a sweeper that pings every creature adds two to each hit at once. It does nothing for combat, nothing for creatures' abilities, and nothing for splashed-in colors, which is why it lives at the artifact slot: the colorless body is the only concession to flexibility in an otherwise mono-red-incentivizing card. It is a build-around stat-line for the spell-slinger archetype, priced at five mana so that you have to mean it before the amplifier comes online.