Shrine of Burning Rage

Two mana buys an empty threat, and that is the whole bet: a payoff that does nothing until you have already committed to slinging red spells. The charge counters come from two sources, an upkeep tick and a cast-trigger on every red spell, which means the artifact accrues at exactly the pace a burn deck sets anyway. A turn where you cast two red spells and untap is a turn where this gains three counters, and the activated ability converts that stored value into a single point-anywhere burst. The design tension lives in the activation cost: three mana plus the tap plus the sacrifice is a steep toll, so the payoff is patience banked and then cashed out all at once, usually to push the last chunk of damage through a stabilized board or to reach a player who has tucked behind blockers. It is reach and inevitability folded into an artifact, immune to creature removal, parked on the battlefield growing while the opponent worries about more immediate threats. The reward for building around it is real, but it tolerates no half-measures: a deck that is not already a red-spell engine never accrues enough counters to make the sacrifice worth a card.