Morophon, the Boundless + Cavern Harpy

Morophon, the Boundless

Cavern Harpy

How it works

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

This clever loop relies on Morophon, the Boundless acting as a cost reducer—by naming Sliver or any other creature type that Cavern Harpy shares, Morophon’s static ability reduces the Harpy's colored mana cost by {W}{U}{B}{R}{G}. Because Cavern Harpy's mana cost is just {U}{B}, this completely eliminates its cost, allowing you to cast it for free. As Cavern Harpy enters the battlefield, its triggered ability forces you to return a blue or black creature to your hand; since the Harpy is itself blue, it can target itself. This creates a self-sustaining cycle that generates infinite creature leaves-the-battlefield triggers, enters-the-battlefield triggers, and storm count without ever needing to spend its alternative life-bouncing cost.