Activate Viscera Seer by sacrificing Selesnya Sanctuary.
When Selesnya Sanctuary dies, Toph, Hardheaded Teach triggers, returning Selesnya Sanctuary from your graveyard to the battlefield tapped.
When Selesnya Sanctuary 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 Viscera Seer ability
Repeat.
This clever engine transforms your non-token artifacts into lands through Toph, the First Metalbender, turning cheap artifact casts into a continuous source of land-based triggers. Once you cast an artifact for free, Toph, Hardheaded Teacher earthbends Selesnya Sanctuary into a creature, allowing you to feed it to Viscera Seer. Because Selesnya Sanctuary is treated as a land by Toph, the First Metalbender, its own entry trigger forces it to bounce that very same artifact back to your hand instead of a traditional land, ready to be recast and repeat the entire loop endlessly for infinite sacrifices and triggers.