Archmage of Echoes + Riptide Laboratory + Timestream Navigator

Mana needed: {1}{U} available the first turn, with {4}{U}{U}{U}{U} each following turn

U identity

Commander legal

The 3 combo pieces

• Archmage of Echoes
• Riptide Laboratory
• Timestream Navigator

What must be in place

You have the city's blessing, and/or control (at least) eight permanents

How to execute it

1. Cast Timestream Navigator by paying {1}{U}.
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 {1}{U} 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 {2}{U}{U}, tapping it and putting on the bottom of your library, causing you to take an extra turn after that one.
7. Repeat.

What the combo produces

• Infinite turns
• Lock