Activate Altar of Dementia by sacrificing Azorius Chancery.
When Azorius Chancery dies, Toph, Hardheaded Teach triggers, returning Azorius Chancery from your graveyard to the battlefield tapped.
When Azorius Chancery enters, it triggers, returning the artifact cast in step 1 from the battlefield to your hand, as it's a land due to Toph, the First Metalbender.
Resolve the Altar of Dementia ability
Repeat.
This clever loop turns the battlefield into an engine of endless reclamation by bridging artifact synergy with land mechanics. With Toph, the First Metalbender redefining your nontoken artifacts as lands, you can cast a zero-mana artifact to trigger Toph, Hardheaded Teacher's earthbend ability and animate Azorius Chancery into a creature. From there, you sacrifice that animated land to Altar of Dementia to mill an opponent, letting Toph, Hardheaded Teacher's safety net return the land straight to the battlefield. Finally, Azorius Chancery’s own entry trigger forces it to return your original artifact back to your hand, resetting the loop for infinite sacrifices, triggers, and milling.