Tap Civic Guildmage for {U} to put Wormfang Manta on top of your library.
Wormfang Manta's LTB triggers, granting you an extra turn after this one.
At the beginning of your end step, Whisperwood Elemental triggers, manifesting Wormfang Manta.
Pay {5}{U}{U} to turn it face up.
Repeat for infinite turns.

Infinite turns

Skip your draw step

Wormfang Manta

Whisperwood Elemental

Civic Guildmage

Tap Civic Guildmage for {U} to put Wormfang Manta on top of your library.
Wormfang Manta's LTB triggers, granting you an extra turn after this one.
Activate Mastery of the Unseen for {3}{W} to manifest Wormfang Manta.
Pay {5}{U}{U} to turn it face up.
Repeat for infinite turns.

Combos with "Civic Guildmage"