ETB Doubler

Passive replacement effects that double your enter-the-battlefield triggers, so each ETB ability of a permanent you control fires an extra time. Panharmonicon doubles artifact and creature ETBs, Yarok, the Desecrated doubles all permanent ETBs, Naban, Dean of Iteration narrows it to Wizards, Starfield Vocalist and Gandalf the White double any permanent entering (Gandalf also leaving), and Elesh Norn, Mother of Machines doubles your ETBs while shutting off your opponents'. The universal doubler (Mirror Room // Fractured Realm, which doubles every triggered ability of your permanents) is included as a strict superset. The payoff staples of blink and ETB-value decks. Distinct from activated.ability_copy (Strionic Resonator, Lithoform Engine), which actively copies a triggered ability on the stack, and from type-scoped trigger doublers like Harmonic Prodigy or Isshin, Two Heavens as One that amplify other trigger types only.