Activate Scorched Rusalka by paying {R} and sacrificing Dire Fleet Hoarder.
Dire Fleet Hoarder triggers, creating a treasure token.
Resolve the Dire Fleet Hoarder's undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Intruder Alarm triggers, untapping all creatures.
Resolve the Sorched Rusalka trigger, dealing 1 damage to any target.
Activate the treasure token by tapping and sacrificing it, adding {R}.
Activate Soul Diviner by tapping it, removing a +1/+1 counter from Dire Fleet Hoarder.
Repeat.

Infinite damage

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite creature sacrifice triggers

Scorched Rusalka

Dire Fleet Hoarder

Mikaeus, the Unhallowed

Soul Diviner

Intruder Alarm

Activate Scorched Rusalka by paying {R} and sacrificing Dire Fleet Hoarder.
Dire Fleet Hoarder and Luminous Broodmoth triggers.
Resolve the Dire Fleet Hoarder triggers, creating a treasure token.
Resolve the Luminous Broodmoth triggers, returning Dire Fleet Hoarder to the battlefield with a flying counter on it.
Intruder Alarm triggers, untapping all creatures.
Resolve the Sorched Rusalka trigger, dealing 1 damage to any target.
Activate the treasure token by tapping and sacrificing it, adding {R}.
Activate Soul Diviner by tapping it, removing a flying counter from Dire Fleet Hoarder.
Repeat.

Luminous Broodmoth

Combos with "Dire Fleet Hoarder"