Activate Altar of Dementia by sacrificing Eternal Witness.
Eternal Witness dies, triggering Deathrender, putting Gravedigger from your hand onto the battlefield and attaching Deathrender to it.
Gravedigger enters the battlefield, returning Eternal Witness from your graveyard to your hand.
Resolve the Altar of Dementia ability from step 1, causing target player to mill cards equal to Eternal Witness' power.
Activate Altar of Dementia by sacrificing Gravedigger.
Gravedigger dies, triggering Deathrender, putting Eternal Witness from your hand onto the battlefield and attaching Deathrender to it.
Eternal Witness enters the battlefield, returning Gravedigger from your graveyard to your hand.
Resolve the Altar of Dementia ability from step 5, causing target player to mill cards equal to Gravedigger's power.
Repeat.

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite mill

Infinite sacrifice triggers

Infinite self-mill

Deathrender

Gravedigger

Eternal Witness

Altar of Dementia

Activate Phyrexian Altar by sacrificing Eternal Witness, adding one mana of any color.
Eternal Witness dies, triggering Deathrender, putting Gravedigger from your hand onto the battlefield and attaching Deathrender to it.
Gravedigger enters the battlefield, returning Eternal Witness from your graveyard to your hand.
Activate Phyrexian Altar by sacrificing Gravedigger, adding one mana of any color.
Gravedigger dies, triggering Deathrender, putting Eternal Witness from your hand onto the battlefield and attaching Deathrender to it.
Eternal Witness enters the battlefield, returning Gravedigger from your graveyard to your hand.
Repeat.

Infinite colored mana

Phyrexian Altar

Activate Ashnod's Altar by sacrificing Eternal Witness, adding {C}{C}.
Eternal Witness dies, triggering Deathrender, putting Gravedigger from your hand onto the battlefield and attaching Deathrender to it.
Gravedigger enters the battlefield, returning Eternal Witness from your graveyard to your hand.
Activate Ashnod's Altar by sacrificing Gravedigger, adding {C}{C}.
Gravedigger dies, triggering Deathrender, putting Eternal Witness from your hand onto the battlefield and attaching Deathrender to it.
Eternal Witness enters the battlefield, returning Gravedigger from your graveyard to your hand.
Repeat.

Infinite colorless mana

Ashnod's Altar

Activate a mana-producing permanent by tapping it, adding at least {1}.
Activate Vizier of Tumbling Sands' cycling ability by paying {0} and discarding it due to New Perspectives.
Escape Protocol and Vizier of Tumbling Sands trigger.
Resolve the Vizier of Tumbing Sands trigger, untapping a mana-producing permanent.
Reoslve the Escape Protocol trigger, blinking Gravedigger.
When Gravedigger enters the battlefield, it triggers, returning Vizier of Tumbing Sands from your graveyard to your hand.
Resolve the cycling ability from step 2, causing you to draw a card.
Repeat.

Infinite card draw

Infinite self-discard triggers

Near-infinite ETB

Infinite draw triggers

Near-infinite LTB

Escape Protocol

Vizier of Tumbling Sands

New Perspectives

Activate Viscera Seer by sacrificing Eternal Witness.
Eternal Witness dies, triggering Deathrender, putting Gravedigger from your hand onto the battlefield and attaching Deathrender to it.
Gravedigger enters the battlefield, returning Eternal Witness from your graveyard to your hand.
Resolve the Viscera Seer ability from step 1, causing you to scry 1.
Activate Viscera Seer by sacrificing Gravedigger.
Gravedigger dies, triggering Deathrender, putting Eternal Witness from your hand onto the battlefield and attaching Deathrender to it.
Eternal Witness enters the battlefield, returning Gravedigger from your graveyard to your hand.
Resolve the Viscera Seer ability from step 5, causing you to scry 1.
Repeat.

Infinite scry 1

Viscera Seer

Activate Gilded Lotus by tapping it, adding {U}{U}{U}.
Activate Mind Over Matter by discarding Gravedigger.
Hashaton triggers, causing you to pay {2}{U} to create a tapped token copy of Gravedigger that is a 4/4 Zombie.
When the Gravedigger token enters the battlefield, it triggers, returning Gravedigger from your graveyard to your hand.
Resolve the Mind Over Matter ability, untapping Gilded Lotus.
Repeat.

Infinite tapped creature tokens

Hashaton, Scarab's Fist

Mind Over Matter

Gilded Lotus

Combos with "Gravedigger"