Activate Ashnod's Altar by sacrificing Shield Sphere.
Activate Salvager of Ruin by sacrificing it, returning Shield Sphere from your graveyard to your hand.
Cast Shield Sphere by paying 0.
Teshar triggers, returning Salvager of Ruin from your graveyard to the battlefield.
Repeat.
This elegant loop turns a humble zero-mana artifact into an infinite engine for colorless mana and death triggers, legal in formats like Commander and Legacy. The magic begins when you use Ashnod's Altar to sacrifice Shield Sphere, generating the two mana needed to keep the machinery humming while sending the Sphere to the graveyard. Salvager of Ruin can then sacrifice itself to retrieve Shield Sphere back to your hand, leaving the Salvager ready to be brought right back. That is where Teshar, Ancestor's Apostle comes in, acting as the ultimate payoff by resurrecting Salvager of Ruin every time you cast a historic spell like Shield Sphere.