Paleontologist's Pick-Axe on the battlefield as Dinosaur Headdress.
Cavalier of Night exiled by Dinosaur Headdress.
({2} magic symbol) available.
Steps
Activate Dinosaur Headdress' equip ability by paying ({2} magic symbol) , attaching it to Priest of Gix and causing Priest of Gix to become a copy of Cavalier of Night.
Activate Altar of Dementia by 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 triggers, adding ({B} magic symbol) ({B} magic symbol) ({B} magic symbol) .
Resolve the Altar of Dementia ability, causing target player to mill cards equal to Priest of Gix's power.