Activate Contagion Engine by paying {4} and tapping it, putting two charge counters on Magistrate's Scepter.
At the beginning of your end step, Atraxa triggers, putting a charge counter on Magistrate's Scepter.
Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, causing you to take an extra turn after this one.
Repeat each turn.

Infinite turns

Atraxa, Praetors' Voice

Magistrate's Scepter

Contagion Engine

Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Magosi to Nesting Grounds.
Activate Magosi's last ability by tapping it, removing an eon counter from it, and returning it from the battlefield to your hand, taking an extra turn after this one.
Play Magosi.
At the beginning of your end step, Atraxa triggers, causing you to proliferate, putting an additional eon counter on Nesting Grounds.
On your next extra turn, activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Nesting Grounds to Magosi.
Repeat from step 2.

Magosi, the Waterveil

Nesting Grounds

At the beginning of your end step, Atraxa triggers, putting an indestructible counter on Myojin.
Activate Myojin by removing an indestructible counter from it, putting five +1/+1 counters on Sage of Hours and the remaining three +1/+1 counters on any creature(s) you control.
Activate Sage of Hours by removing all +1/+1 counters from it, causing you to take an extra turn after this one.
Repeat each turn.

Myojin of Towering Might

Sage of Hours

Activate Avatar Kuruk by paying {20} minus {1} for each creature and/or artifact you can tap while activating it, causing you to take an extra turn after this one.
Activate Baboon Spirit by paying {3}{U}, exiling Avatar Kuruk.
At the beginning of your end step, Atraxa and Baboon Spirit trigger.
Resolve the Baboon Spirit trigger, returning The Legend of Kuruk from exile to the battlefield with a lore counter on it.
The Legend of Kuruk's first chapter ability triggers, causing you to scry 2 and draw a card.
Resolve the Atraxa trigger, causing you to proliferate and put a lore counter on The Legend of Kuruk.
The Legend of Kuruk's second chapter ability triggers, causing you to scry 2 and draw a card.
Move to your next turn. At the beginning of that turn's precombat main phase, The Legend of Kuruk triggers, putting a lore counter on it. The Legend of Kuruk's third chapter ability then triggers, causing you to exile it and return it to the battlefield as Avatar Kuruk.
Repeat.

Combos with "Atraxa, Praetors' Voice"