Sage of Hours + The Ten Rings + Witch-king of Angmar + Stark's Ingenuity

Sage of Hours

The Ten Rings

Witch-king of Angmar

Stark's Ingenuity

How it works

1. If you have six or more cards in hand, activate Witch-king of Angmar by discarding a card.
2. Repeat step 1 until you have five or fewer cards in hand.
3. At the beginning of your end step, The Ten Rings triggers, causing you to draw cards until you have ten cards in your hand.
4. Stark's Ingenuity triggers for each card drawn, putting that many +1/+1 counters on Sage of Hours.
5. Activate Sage of Hours by removing all +1/+1 counters from it, causing you to take at least one extra turn after this one.
6. Repeat each turn.

This clever loop locks in infinite extra turns by turning your end step into an engine of inevitable victory. With The Ten Rings guaranteeing you always refill your hand to ten cards at the end of your turn, Stark's Ingenuity steps in to translate every single card drawn into a +1/+1 counter for Sage of Hours. To make sure you can safely reach that end step while controlling your hand size, you can discard cards to activate Witch-king of Angmar's ability, which also conveniently triggers the Ring tempting you and grants protection. Once Sage of Hours has amassed enough counters, you remove them to take an extra turn, repeating the process indefinitely to completely lock opponents out of the game.