Molten Echoes + Changeling Titan

Molten Echoes

Changeling Titan

How it works

1. Cast Changeling Titan by paying its mana cost.
2. When Changeling Titan enters the battlefield, its champion ability and Molten Echoes triggers.
3. Resolve the Molten Echoes trigger, creating a token copy of Changeling Titan with haste.
4. When the Changeling Titan token enters the battlefiled, its champion ability triggers, exiling the nontoken Changeling Titan until the token Changeling Titan leaves the battlefield.
5. Resolve the champion ability from step 2, exiling the token Changeling Titan.
6. The token Changeling Titan leaves the battlefield, returning the nontoken Changeling Titan from exile to the battlefield.
7. Repeat from step 2.

This loop hinges on a clever recursive relay between the champion mechanic and a tribal enchantment. You cast Changeling Titan, whose all-creature Changeling type naturally satisfies Molten Echoes as it enters. The original Titan's champion trigger tries to exile a creature, but you can respond by letting the Molten Echoes trigger resolve first to spin off a hasty token copy. That token's own champion trigger then eats the original Titan, immediately dropping the token and triggering the whole cycle anew to generate an endless stream of entering and leaving triggers.