Cast Sensei's Divining Top by paying 0 due to Heliod
When Sensei's Divining Top enters, Skyswimmer Koi triggers.
Holding priority, activate Sensei's Divining Top by tapping it, causing you to draw a card and put Sensei's Divining Top on top of your library.
Resolve the Skyswimmer Koi trigger, causing you to draw Sensei's Divining Top from your library, and then discard a card other than Sensei's Divining Top.
Repeat
This clever loop transforms Heliod, the Radiant Dawn // Heliod, the Warped Eclipse into an engine that reduces artifact costs to zero, allowing you to cast Sensei's Divining Top for free. As the Top enters, Skyswimmer Koi triggers to let you draw and discard, but by tapping the Top in response, you can draw a card while putting the Top back onto your library just in time for the Koi's resolution to draw it right back into your hand. Because Heliod's passive cost reduction makes the Top completely free to recast over and over, you can endlessly churn through your deck for infinite looting and a massive storm count.