Karn, the Great Creator, Ugin's Nexus, The Chain Veil, Doubling Season, and Arcbound Ravager

Prerequisites

• Karn, the Great Creator on the battlefield
• Ugin's Nexus on the battlefield
• The Chain Veil on the battlefield
• Doubling Season on the battlefield
• Arcbound Ravager on the battlefield
• on the first turn, with available each subsequent turn available

Steps

1. Activate Arcbound Ravager by sacrificing Ugin's Nexus
2. Ugin's Nexus is exiled instead of being put into your graveyard, and causes you to take an extra turn after this one
3. Resolve the Arcbound Ravager ability, putting two +1/+1 counters on it
4. Activate The Chain Veil by paying and tapping it, allowing you an additional activation of your planeswalkers' loyalty abilities this turn
5. Activate Karn's first loyalty ability by putting two loyalty counters on it, causing any artifact to become an artifact creature until end of turn
6. Activate Karn's second loyalty ability by removing two loyalty counters from it, revealing Ugin's Nexus from exile and putting it into your hand
7. Move to your next turn
8. Cast Ugin's Nexus by paying
9. Repeat

Results

• Infinite turns