During an opponent's turn, activate Relic of Legends' second ability by tapping The Watcher, adding {U}.
Activate Drowned Rusalka by paying {U} and sacrificing a Tentacle.
When the Tentacle dies, The Watcher's second ability triggers, untapping itself.
Resolve the Drowned Rusalka trigger, causing you to rummage.
The Watcher's first ability triggers, creating a 1/1 Tentacle creature token.
Repeat.

Infinite draw triggers

Infinite rummaging

Infinite self-discard triggers

Near-infinite death triggers

Near-infinite creature ETB

Near-infinite creature LTB

Near-infinite creature sacrifice triggers

The Watcher in the Water

Drowned Rusalka

Relic of Legends

Activate Drowned Rusalka by paying {U} and sacrificing another creature, causing you to rummage.
The Locust God triggers, creating a 1/1 Insect creature token with flying and haste.
Activate the Insect by tapping it, adding {U}.
Repeat.

The Locust God

Cryptolith Rite

During an opponent's turn, activate Earthcraft by tapping The Watcher, untapping a basic Island you control.
Activate the Island by tapping it, adding {U}.
Activate Drowned Rusalka by paying {U} and sacrificing a Tentacle.
When the Tentacle dies, The Watcher's second ability triggers, untapping itself.
Resolve the Drowned Rusalka trigger, causing you to rummage.
The Watcher's first ability triggers, creating a 1/1 Tentacle creature token.
Repeat.

Earthcraft

Activate a basic Island by tapping it, adding {U}.
Activate Drowned Rusalka by paying {U} and sacrificing another creature, causing you to rummage.
The Locust God triggers, creating a 1/1 Insect creature token with flying and haste.
Activate Earthcraft by tapping the Insect, untapping the basic Island.
Repeat.

Combos with "Drowned Rusalka"