Magosi, the Waterveil + Out of the Tombs + Nesting Grounds

Prerequisites

Magosi is untapped.

Steps

1. At the beginning of your upkeep, Out of the Tombs triggers, putting two eon counters on itself, then milling cards equal to the number of eon counters on it.
2. Activate Nesting Grounds by paying {1} and tapping it, moving an eon counter from Out of the Tombs to Magosi.
3. Activate Magosi by tapping it, removing an eon counter from it, and returning it to your hand, causing you to take an extra turn after this one.
4. In your main phase, play Magosi.
5. Go to your next turn.
6. Repeat.