Summon Herald of Mirages, no other active effects on the field
Either attack into an opponent's monster or be attacked on the next turn
No trigger to search cards when it is sent to the grave
Opponent uses Faustian bargain to send to grave and summon
No trigger when sent to grave
Herald of Mirages is destroyed by opponents card effect
No trigger when sent to grave

Replay attached shows all 3 situations on 3 different turns to circumvent the hard once per turn clause.
(Faustian Bargain turn 2, Fissure turn 4, destruction by battle turn 6)
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Herald of Mirages Search in the Graveyard, not the deck
There is no Ritual card in your GY in your replay, so Herald of mirage have nothing to recover, so it cannot activate (since it is not a mandatory effect)