Sensei's Divining Top + Herald of Kozilek + Skyswimmer Koi

Sensei's Divining Top

Herald of Kozilek

Skyswimmer Koi

How it works

1. Cast Sensei's Divining Top by paying 0 due to Herald of Kozilek.
2. When Sensei's Divining Top enters, Skyswimmer Koi triggers.
3. 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.
4. 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.
5. Repeat

This clever loop turns the unassuming Sensei's Divining Top into an engine of endless motion by exploiting the cost reduction provided by Herald of Kozilek. Because the Top normally costs one mana to cast, the Herald makes it entirely free, allowing you to redeploy it the moment it leaves the battlefield. Meanwhile, Skyswimmer Koi acts as your catalyst, watching for artifacts to arrive and fueling your hand by letting you draw and discard on demand. By responding to the Koi's entry trigger with the Top's own tapping ability, you draw a card and slide the Top back to the top of your library just in time for the Koi's trigger to draw it right back out into your hand.