The Sixth Doctor + Karn's Temporal Sundering + Isochron Scepter + Reprieve

The Sixth Doctor

Karn's Temporal Sundering

Isochron Scepter

Reprieve

How it works

1. Cast Karn's Temporal Sundering by paying 4.
2. The Sixth Doctor triggers, copying Karn's Temporal Sundering.
3. Resolve the copy of Karn's Temporal Sundering, causing you to take an extra turn after this one.
4. Holding priority, activate Isochron Scepter by paying 2 and tapping it, casting a copy of Reprieve without paying its mana cost.
5. Resolve Reprieve, returning the original Karn's Temporal Sundering to your hand and causing you to draw a card.
6. Repeat each turn.

This cunning loop hinges on the synergy between The Sixth Doctor and Karn's Temporal Sundering, allowing you to continually take extra turns while keeping your primary win-con safe in hand. By leveraging Isochron Scepter imprinted with Reprieve, you can bounce the original Karn's Temporal Sundering back to your hand every single turn after its copy has resolved, netting an extra turn and avoiding exile. Reprieve simultaneously replaces itself by drawing you a card, ensuring you never run out of gas while chaining these legendary spells indefinitely.