Combat Celebrant + Displacer Kitten + Spellbinder + Fervor

Combat Celebrant

Displacer Kitten

Spellbinder

Fervor

How it works

1. Declare Combat Celebrant and the creature with Spellbinder attached as attackers, choosing to exert Combat Celebrant as it attacks.
2. Combat Celebrant triggers, causing you to untap all other creatures you control and to get an additional combat phase after this one.
3. Deal combat damage using the creature that has Spellbinder attached.
4. Spellbinder triggers, causing you to copy a card exiled with it, and cast the copy without paying its mana cost.
5. Displacer Kitten triggers, blinking Combat Celebrant.
6. Resolve the spell cast in step 4.
7. Repeat each combat phase.

This dazzling engine hinges on Combat Celebrant's ability to grant infinite combat phases by being exerted upon attack, while Fervor ensures it can dive right back into the fray with haste each time. To sustain this loop, the equipped creature deals combat damage to trigger Spellbinder, casting a copied instant spell without paying its mana cost. That noncreature spell triggers Displacer Kitten, whose blink ability resets Combat Celebrant by exiling and returning it to the battlefield, clearing its exertion status so it can attack and exert all over again.