Timestream Navigator, Riptide Laboratory, and Archmage of Echoes

Prerequisites

• Timestream Navigator in hand
• Riptide Laboratory on the battlefield
• Archmage of Echoes on the battlefield
• You have the city's blessing, and/or control (at least) eight permanents available the first turn, with each following turn available

Steps

1. Cast Timestream Navigator by paying
2. Archmage of Echoes triggers, copying the Timestream Navigator spell
3. Resolve both Timestream Navigator spells
4. If you don't have the city's blessing, either the Timestream Navigator token or the nontoken Timestream Navigator gives you the city's blessing
5. During your next turn, activate Riptide Laboratory's second ability by paying and tapping it, returning the nontoken Timestream Navigator to your hand from the battlefield
6. Activate the ability of the Timestream Navigator token by paying , tapping it and putting on the bottom of your library, causing you to take an extra turn after that one
7. Repeat

Results

• Infinite turns