Activate City of Traitors by tapping it, adding {C}{C}.
Activate Silvanus's Invoker by paying {1}, untapping City of Traitors and causing it to become an 8/8 Elemental with trample and haste in addition to its other types until end of turn.
Repeat.
Once you have infinite mana, you may tap and untap any other land(s) you control, and if you control lands that can produce {R} and {G}, use the mana to activate Agatha of the Vile Cauldron's ability.

Infinite colorless mana

Infinite power and toughness for most creatures you control until end of turn

Infinite mana lands you control can produce

Infinite untap of lands you control

Agatha of the Vile Cauldron

Silvanus's Invoker

City of Traitors

Activate City of Traitors by tapping it, adding six {C} due to Nyxbloom Ancient.
Activate Portent Tracker by tapping it, untapping City of Traitors
Activate Staff of Domination's third ability by paying {3} and tapping it, untapping Portent Tracker.
Activate Staff of Domination's first ability by paying {1}, untapping it.
Repeat.

Infinite card draw

Infinite draw triggers

Infinite lifegain

Infinite lifegain triggers

Infinite mana creatures you control can produce

Infinite untap of creatures you control

Staff of Domination

Nyxbloom Ancient

Portent Tracker

Cast Staff of Domination by paying {3}.
Toph, Hardheaded Teacher triggers, earthbending City of Traitors.
Cast Marvin by paying {2}.
Toph, Hardheaded Teacher triggers, earthbending Staff of Domination.
At the beginning of your end step, Toph, the First Metalbender triggers, earthbending Marvin, thus giving it haste.
Activate Marvin using City of Traitors's ability by tapping it, adding {C}{C}
Activate Marvin using Staff of Domination's first ability by paying {1}, untapping Marvin.
Repeat from step 6.

Marvin, Murderous Mimic

Toph, Hardheaded Teacher

Toph, the First Metalbender

Combos with "City of Traitors"