Activate Shilgengar by sacrificing Simic Growth Chamber.
When Simic Growth Chamber dies, Toph, Hardheaded Teach triggers, returning Simic Growth Chamber from your graveyard to the battlefield tapped.
When Simic Growth Chamber 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 Shilgengar ability
Repeat.
This fascinating loop turns your cheap artifact into a perpetual motion machine by leveraging Toph, the First Metalbender to permanently reclassify nontoken artifacts as lands. With that foundation set, casting your artifact triggers Toph, Hardheaded Teacher to earthbend Simic Growth Chamber into an animate land creature, which Shilgengar, Sire of Famine can then sacrifice to churn out Blood tokens. Because Simic Growth Chamber dies, its land-creature transformation triggers Toph, Hardheaded Teacher's safety net to return it straight to the battlefield, where its own entry trigger bounces your original artifact right back to your hand to start the cycle anew.