Activate five in any combination of Forests, Mountains and Plains by tapping them, adding {5}.
Keeper of Progenitus triggers five times, adding at least {5}.
Activate Magus of the Candelabra by paying {5} and tapping it, untapping the five lands.
Activate Staff of Domination's third ability by paying {3} and tapping it, untapping Magus of the Candelabra.
Activate Staff of Domination's first ability by paying {1}, untapping Staff of Domination.
Repeat.
Once you have infinite mana, you may use it to activate Staff of Domination's other abilities.

Infinite card draw

Infinite draw triggers

Infinite lifegain

Infinite lifegain triggers

Infinite mana creatures you control can produce

Infinite mana lands you control can produce

Infinite untap of creatures you control

Infinite untap of lands you control

Magus of the Candelabra

Staff of Domination

Keeper of Progenitus

Activate two lands by tapping them, adding at least {2}.
Keeper of Progenitus triggers twice, adding {2}.
Activate Magus of the Candelabra by paying {3} and tapping it, untapping the two lands and Magus of the Candelabra.
Repeat.

Infinite green mana

Ashaya, Soul of the Wild

Activate Pili-Pala by tapping it, adding {G}{G}.
Activate Pili-Pala by paying {2} and untapping it, adding one mana of any color.
Repeat.

Infinite colored mana

Pili-Pala

Declare Overlord of the Hauntwoods as an attacker.
Overlord of the Hauntwoods triggers, creating an untapped Everywhere land token due to Spelunking.
When the Everywhere token enters the battlefield, Springheart Nantuko triggers.
Holding priority, activate Everywhere by tapping it, adding {G}.
Keeper of Progenitus triggers, adding {G}.
Resolve the Springheart Nantuko trigger, causing you to pay {1}{G} to create a token copy of Overlord of the Hauntwoods.
When the Overlord of the Hauntwoods token enters the battlefield, it triggers, creating a tapped Everywhere land token.
Repeat from step 3.

Infinite ETB

Infinite creature tokens

Infinite landfall triggers

Infinite tapped Mountain tokens

Infinite tapped Island tokens

Infinite tapped Forest tokens

Infinite tapped Everywhere land tokens

Infinite tapped Plains tokens

Infinite tapped Swamp tokens

Springheart Nantuko

Overlord of the Hauntwoods

Spelunking

Play a land. When the land enters, Springheart Nantuko triggers, causing you to pay {1}{G} to create a token copy of Dryad Arbor.
When the Dryad Arbor token enters, Springheart Nantuko triggers. Holding priority, activate the Dryad Arbor token by tapping it, adding {G}.
Keeper of Progenitus triggers, adding {G}.
Resolve the Springheart Nantuko trigger, causing you to pay {1}{G} to create a token copy of Dryad Arbor.
Repeat from step 2.

Infinite tapped creature tokens

Dryad Arbor

Thousand-Year Elixir

Activate Fertilid, searching your library for a basic Forest card, putting it onto the battlefield tapped.
Amulet of Vigor triggers, untapping the land.
Retreat to Kazandu triggers, putting a +1/+1 counter Fertilid.
Tap the land for {G}{G}.
Repeat.

Near-infinite landfall triggers

Put all basic Forests from your library onto the battlefield

Fertilid

Amulet of Vigor

Retreat to Kazandu

Activate Fertilid, searching your library for a basic Forest card, putting it onto the battlefield tapped.
Amulet of Vigor triggers, untapping the land.
Felidar Retreat triggers.
Resolve the Felidar Retreat trigger putting a +1/+1 counter on each creature you control.
Tap the land for {G}{G}.
Repeat.

Near-infinite +1/+1 counters on creatures you control

Felidar Retreat

Activate Staff of Domination by tapping it, adding {G} as it's a Forest land due to Toph and Yavimaya.
Keeper of Progenitus triggers, adding {G}.
Activate Staff of Domination's first ability by paying {1}, untapping it.
Repeat.

Toph, the First Metalbender

Yavimaya, Cradle of Growth

Combos with "Keeper of Progenitus"