Activate Viscera Seer by sacrificing Cavalier of Night.
When Cavalier of Night dies, it triggers, returning Activated Sleeper from your graveyard to the battlefield as a copy of Cavalier of Night.
When Activated Sleeper enters the battlefield, it triggers; choose not to sacrifice a creature.
Activate Viscera Seer by sacrificing Activated Sleeper.
When Activated Sleeper dies, it triggers, returning Activated Sleeper from your graveyard to the battlefield as a copy of Cavalier of Night.
When Activated Sleeper enters the battlefield, it triggers; choose not to sacrifice a creature.
Resolve the Viscera Seer ability from step 4, causing you to scry 1.
Repeat from step 4.

Infinite death triggers

Infinite ETB

Infinite LTB

Infinite sacrifice triggers

Infinite scry 1

Cavalier of Night

Activated Sleeper

Viscera Seer

Activate Altar of Dementia by sacrificing Glasspool Mimic.
When Glasspool Mimic dies, its second ability triggers, returning itself to the battlefield as a copy of Cavalier of Night.
When Glasspool Mimic enters the battlefield, its first ability triggers, choose not to sacrifice a creature.
Resolve the Altar of Dementia ability, causing target player to mill cards equal to Glasspool Mimic's power.
Repeat.

Infinite mill

Infinite self-mill

Glasspool Mimic // Glasspool Shore

Altar of Dementia

Activate Ashnod's Altar by sacrificing Phantasmal Image, adding {C}{C}.
When Phantasmal Image dies, its last ability from Cavalier of Night triggers, returning itself from your graveyard to the battlefield as a copy of Cavalier of Night.
When Phantasmal Image enters the battlefield, its first triggered ability from Cavalier of Night triggers; choose not to sacrifice a creature.
Repeat.

Infinite colorless mana

Phantasmal Image

Ashnod's Altar

Activate Altar of Dementia by sacrificing The Master.
When The Master dies, its second ability triggers, returning itself from your graveyard to the battlefield as a copy of Cavalier of Night.
When The Master enters the battlefield, its first ability triggers, doing nothing.
Resolve the Altar of Dementia ability, causing target player to mill cards equal to The Master's power.
Repeat.

The Master, Formed Anew

Activate Altar of Dementia by sacrificing Mirror Image.
When Mirror Image dies, its last ability from Cavalier of Night triggers, returning itself from your graveyard to the battlefield as a copy of Cavalier of Night.
When Mirror Image enters the battlefield, its first triggered ability from Cavalier of Night triggers; choose not to sacrifice a creature.
Resolve the Altar of Dementia ability from step 1.
Repeat.

Mirror Image

Activate Dinosaur Headdress' equip ability by paying {2}, attaching it to Priest of Gix and causing Priest of Gix to become a copy of Cavalier of Night.
Activate Blasting Station by tapping it and sacrificing Priest of Gix.
When Priest of Gix dies, its second ability triggers, returning itself from your graveyard to the battlefield.
When Priest of Gix enters the battlefield, it and Blasting Station trigger.
Resolve the Priest of Gix trigger, adding {B}{B}{B}.
Resolve the Blasting Station trigger from step 4, untapping it.
Resolve the Blasting Station ability from step 2, 
Repeat.

Combos with "Cavalier of Night"