Activate the Merfolk by tapping it.
Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
When the Merfolk enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Resolve the Merfolk's tap ability.
Repeat.

Infinite ETB

Infinite creature tokens

Infinite untap of creatures

Infinite mana creatures you control can produce

Infinite instances of the tapped creature's ability

Infinite untap of creatures you control

Merfolk Creature With Free Tap Ability

Intruder Alarm

Deeproot Pilgrimage

Activate Kumena's first ability by tapping another nontoken Merfolk you control.
Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
When the Merfolk enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Resolve the Kumena ability, causing it to be unable to be blocked this turn.
Repeat.
You may activate Kumena's other abilities instead once you control enough Merfolks to do so, ensuring to tap at least one nontoken Merfolk each activation.

Infinite card draw

Infinite draw triggers

Infinite +1/+1 counters on creatures you control

Merfolk Creature

Kumena, Tyrant of Orazca

Activate Mutavault's second ability by paying {1}, causing it to become a 2/2 creature with all creature types until end of turn.
Activate Mutavault's first ability by tapping it, adding {C}.
Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
When the Merfolk enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Repeat from step 2.

Infinite colorless mana

Mutavault

Activate Earthcraft by tapping a nontoken Merfolk you control, targeting any basic land.
Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
When the Merfolk enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Resolve the Earthcraft ability, untapping the basic land.
If you controlled the basic land, you may activate it by tapping it, adding {1}.
Repeat.

Infinite mana basic lands you control can produce

Infinite untap of basic lands you control

Earthcraft

Activate Firdoch Core's first ability by tapping it, adding one mana of any color.
Deeproot Pilgrimage triggers. Holding priority, activate Firdoch Core's second ability by paying {4}, causing it to become a 4/4 artifact creature until end of turn.
Resolve the Deeproot Pilgrimage trigger, creating a 1/1 Merfolk creature token.
When the Merfolk enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Activate Firdoch Core's first ability by tapping it, adding one mana of any color.
Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
Repeat from step 4.

Infinite colored mana

Firdoch Core

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