During an opponent's turn, activate Mothdust Changeling by tapping a blue creature you control except Unctus.
The creature triggers, causing you to loot.
The Watcher's first ability triggers, creating a 1/1 Tentacle creature token.
Resolve the Mothdust Changeling ability.
Repeat.

Infinite self-discard triggers

Near-infinite ETB

Infinite draw triggers

Infinite looting

Near-infinite tapped creature tokens

Unctus, Grand Metatect

The Watcher in the Water

Mothdust Changeling

Cast Mothdust Changeling by paying {U}.
Mothdust Changeling enters the battlefield, triggering Cloudstone Curio and Lathliss.
Resolve the Cloudstone Curio trigger, choosing not to return anything to your hand from the battlefield.
Resolve the Lathliss trigger, creating a 5/5 Dragon creature token.
The Dragon enters the battlefield, triggering Cloudstone Curio, returning Mothdust Changeling from the battlefield to your hand.
Activate Phyrexian Altar by sacrificing the Dragon token, adding {U}.
Repeat.

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite sacrifice triggers

Infinite storm count

Lathliss, Dragon Queen

Cloudstone Curio

Phyrexian Altar

Cast Mothdust Changeling by paying {U}.
Mothdust Changeling enters the battlefield, triggering Cloudstone Curio and Miirym.
Resolve the Cloudstone Curio trigger, choosing not to return anything to your hand from the battlefield.
Resolve the Miirym trigger, creating a token copy of Mothdust Changeling.
The Mothdust Changeling token enters the battlefield, triggering Cloudstone Curio, returning the nontoken Mothdust Changeling from the battlefield to your hand.
Activate Phyrexian Altar by sacrificing the Mothdust Changeling token, adding {U}.
Repeat.

Miirym, Sentinel Wyrm

Cast Mothdust Changeling by paying {U}.
When Mothdust Changeling enters the battlefield, Cloudstone Curio and Bladewing's Thrall trigger.
Resolve the Cloudstone Curio trigger, choosing to return nothing to your hand.
Resolve the Bladewing's Thrall trigger, returning it from your graveyard to the battlefield.
When Bladewing's Thrall enters the battlefield, Cloudstone Curio triggers, returning Mothdust Changeling from the battlefield to your hand.
Activate Phyrexian Altar by sacrificing Bladewing's Thrall, adding {U}.
Repeat.

Bladewing's Thrall

Activate Bog Glider by tapping it and sacrificing Mothdust Changeling.
Holding priority, activate Hua Tuo by tapping it, putting Mothdust Changeling on top of your library from your graveyard.
Resolve the Bog Glider ability, searching your library for Mothdust Changeling and putting it onto the battlefield.
When Mothdust Changeling enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Repeat.

Infinite landfall triggers

Infinite mana creatures you control can produce

Infinite untap of creatures

Infinite untap of creatures you control

Bog Glider

Ashaya, Soul of the Wild

Intruder Alarm

Hua Tuo, Honored Physician

Activate Bog Glider by tapping it and sacrificing Mothdust Changeling.
When Mothdust Changeling dies, Mortuary triggers, putting the creature on top of your library from your graveyard.
Resolve the Bog Glider ability, searching your library for Mothdust Changeling and putting it onto the battlefield.
When Mothdust Changeling enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Repeat.

Mortuary

Combos with "Mothdust Changeling"