Urza, Prince of Kroog, Timestream Navigator, and Thran Forge

Prerequisites

• Urza, Prince of Kroog on the battlefield
• Timestream Navigator on the battlefield
• Thran Forge on the battlefield
• You have the city's blessing
• Timestream Navigator does not have summoning sickness
• each turn available

Steps

1. Activate Thran Forge by paying , causing Timestream Navigator to get +1/+0 and become an artifact until end of turn
2. Activate Urza by paying , creating a token copy of Timestream Navigator that is a 1/1 Soldier creature
3. Activate the oldest Timestream Navigator by paying , tapping it and putting it on the bottom of your library from the battlefield, causing you to take an extra turn after this one
4. Repeat each turn

Results

• Infinite turns