Activate Coastal Hornclaw by sacrificing Orzhov Basilica.
When Orzhov Basilica dies, Toph, Hardheaded Teach triggers, returning Orzhov Basilica from your graveyard to the battlefield tapped.
When Orzhov Basilica 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 Coastal Hornclaw ability
Repeat.
This clever loop turns the battlefield into an engine of endless iteration by weaponizing land types and sacrifice. With Toph, the First Metalbender actively transforming your nontoken artifacts into lands, your zero-cost artifact becomes the ultimate recyclable fodder for Orzhov Basilica. Coastal Hornclaw acts as the sacrificial outlet that bins Orzhov Basilica, whose subsequent death triggers the earthbend resurrection from Toph, Hardheaded Teacher. As Orzhov Basilica re-enters the battlefield, its own triggered ability forces you to return a land to your hand—and thanks to the type-changing magic of Toph, the First Metalbender, that zero-cost artifact is a legal and vulnerable target, returning safely to your hand so you can cast it all over again and fuel the entire cycle indefinitely.