At the beginning of your combat phase, Deepfathom Echo triggers, causing it to explore and become a copy of Kiora's Follower until end of turn.
Activate Kiora's Follower by tapping it, targeting Deepfathom Echo.
Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
Resolve the Kiora's Follower ability, untapping Deepfathom Echo.
Activate Deepfathom Echo by tapping it, targeting Kiora's Follower.
Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
Resolve the Deepfathom Echo ability, untapping Kiora's Follower.
Repeat from step 2.

Infinite ETB

Infinite creature tokens

Deeproot Pilgrimage

Deepfathom Echo

Kiora's Follower

Cast Deepfathom Echo by paying its mana cost, choosing to have it enter the battlefield as a copy of Abdel Adrian.
Put the original Abdel Adrian into your graveyard due to the legend rule, causing Karmic Guide to return to the battlefield from exile.
Karmic Guide and Deepfathom Echo's abilities trigger.
Resolve the Deepfathom Echo ability, choosing to exile Karmic Guide until Deepfathom Echo leaves the battlefield and creating a 1/1 Soldier creature token.
Resolve the Karmic Guide trigger, returning Abdel Adrian from your graveyard to the battlefield.
Put Deepfathom Echo into your graveyard due to the legend rule, causing Karmic Guide to return to the battlefield from exile.
Karmic Guide and Abdel Adrian's abilities trigger.
Resolve the Abdel Adrian ability, exiling Karmic Guide until Abdel Adrian leaves the battlefield and creating a 1/1 Soldier creature token.
Resolve the Karmic Guide trigger, returning Deepfathom Echo from your graveyard to the battlefield as a copy of Abdel Adrian.
Repeat from step 2.

Combos with "Deepfathom Echo"