Kentaro, the Smiling Cat + Cavern Harpy + Urza's Incubator + Conspiracy

Kentaro, the Smiling Cat

Cavern Harpy

Urza's Incubator

Conspiracy

How it works

1. Cast Cavern Harpy by paying 0.
2. When Cavern Harpy enters the battlefield, it triggers, returning itself from the battlefield to your hand.
3. Repeat.

By letting Conspiracy redefine every creature as a Samurai, we unlock a clever cost-reduction engine built on Kentaro, the Smiling Cat and Urza's Incubator. Kentaro allows you to cast your Samurai spells by paying their mana value as generic mana ({X}), while Urza's Incubator slashes that cost by {2}, making any creature with a mana value of 2 or less entirely free to cast. When you apply this discount to Cavern Harpy, its blue and black color identity doesn't stop Kentaro from reducing its cost to zero; once it enters the battlefield, its own triggered ability forces it right back to your hand so you can recast it endlessly.