Energy Doubler

Cards that pour out {E} energy counters through wide, recurring triggers keyed to events beyond their own arrival, building the surplus that fuels an energy engine. Gonti's Aether Heart gives {E}{E} whenever an artifact you control enters, and Aetherworks Marvel adds {E} whenever a permanent you control goes to the graveyard, scaling far past a single ETB. Narrower view of Energy Producer, the umbrella for all cards that make {E}; this covers the heavy, board-wide accumulators rather than one-shot or self-only sources that produce energy on their own enter-the-battlefield or combat triggers. Distinct from Energy Payoff, which spends stockpiled {E} for hexproof, tokens, or free spells instead of generating it.