Riku of Two Reflections + Narset's Reversal + Karn's Temporal Sundering

Riku of Two Reflections

Narset's Reversal

Karn's Temporal Sundering

How it works

1. Cast Karn's Temporal Sundering by paying 4.
2. Riku's first ability triggers - choose not to pay.
3. Holding priority, cast Narset's Reversal by paying , targeting Karn's Temporal Sundering.
4. Riku's first ability triggers, causing you to pay to copy Narset's Reversal, with the copy targeting the original Narset's Reversal.
5. Resolve the copy of Narset's Reversal, copying the original Narset's Reversal targeting Karn's Temporal Sundering, and returning the original Narset's Reversal to your hand.
6. Resolve the copy of Narset's Reversal created in step 5, copying Karn's Temporal Sundering and returning the original Karn's Temporal Sundering to your hand.
7. Resolve Karn's Temporal Sundering, causing you to take an extra turn after this one.
8. Repeat each turn.

This clever spell-loop centers around casting Karn's Temporal Sundering to claim extra time, leveraging a legendary creature presence to satisfy its casting restriction. Before it resolves, you loop Narset's Reversal back to your hand while continuously copying it, ensuring you never actually lose access to either spell. The secret catalyst making this recursion possible is Riku of Two Reflections, whose triggered ability provides the exact mana-fueled duplication needed to keep the bounce chain alive indefinitely.