Muldrotha, the Gravetide + Riptide Shapeshifter + Timestream Navigator

Mana needed: {4}{U}{U}{U}{U} the first turn, with {7} plus six {U} available each extra turn

BGU identity

Commander legal

The 3 combo pieces

• Muldrotha, the Gravetide
• Riptide Shapeshifter
• Timestream Navigator

What must be in place

You have the city's blessing.
Timestream Navigator does not have summoning sickness.
You do not have any Human, Pirate, or Wizard creature cards in your library

How to execute it

1. Activate Timstream Navigator by paying {2}{U}{U}, tapping it and putting it on the bottom of your library, causing you to take an extra turn after this one.
2. Activate Riptide Shapeshifter by paying {2}{U}{U} and sacrificing it, naming any of Timestream Navigator's types, and then revealing Timestream Navigator from your library and putting it onto the battlefield.
3. Move to your next turn.
4. Cast Riptide Shapeshifter from your graveyard by paying {3}{U}{U}.
5. Repeat.

What the combo produces

• Infinite turns
• Lock