Clement, the Worrywort | Shrieking Drake | Cloud of Faeries

(and one other card)

Activate
Nykthos, Shrine to Nyx's last ability by paying ({2} magic symbol) and tapping it, adding at least ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) .
Activate any other land by tapping it, adding ({1} magic symbol) .
Cast
Cloud of Faeries by paying ({1} magic symbol) ({U} magic symbol) .
When
Cloud of Faeries enters the battlefield, it and
Clement trigger.
Resolve the
Clement trigger, choosing to return
Shrieking Drake from the battlefield to your hand.
Resolve the
Cloud of Faeries trigger, untapping the land(s) from step 1 and 2.
Cast
Shrieking Drake by paying ({U} magic symbol) .
When
Shrieking Drake enters the battlefield, it and
Clement trigger.
Resolve the
Shrieking Drake trigger, returning
Cloud of Faeries from the battlefield to your hand.
Resolve the
Clement trigger, choosing to return nothing.
Repeat.

If your devotion to blue is at least four, this also produces infinite mana and infinite untap of lands you control.
If you have a creature with mana value 0 that can survive after being cast for 0 mana, you can bounce it each time in step 9 and also cast it infinite times.