You control two lands that enter the battlefield untapped and produce mana.
Walking Atlas does not have summoning sickness.
({2} magic symbol) , plus enough mana to cast the instant or sorcery available.
Steps
Cast any instant or sorcery by paying its mana cost.
In response, activate Uyo by paying ({2} magic symbol) and returning two lands you control from the battlefield to your hand, copying an instant or sorcery spell.
Activate Walking Atlas by tapping it, putting a land from your hand onto the battlefield.
When the land enters the battlefield, Retreat to Coralhelm triggers, untapping Walking Atlast.
Repeat steps 3 and 4 one additional time.
Activate those lands by tapping them, adding at least ({2} magic symbol) .
Repeat from step 2 any number of times.
Resolve any number of copies created in step 2 and the original spell.
Results
Infinite copies of instant and sorcery spells on the stack.