Activate Phyrexian Altar by sacrificing Archon of Falling Stars, adding one mana of any color.
When Archon of Falling Stars dies, it triggers, returning Necromancy from your graveyard to the battlefield.
When Necromancy enters the battlefield, it triggers, returning Archon of Falling Stars from your graveyard to the battlefield, and attaching Necromancy to it.
Repeat.
This elegant loop operates as a self-sustaining cycle of resurrection and sacrifice, turning the graveyard into a bustling engine. By utilizing Phyrexian Altar, you can feed Archon of Falling Stars to generate mana while simultaneously triggering its demise. That death triggers the Archon's own ability, pulling Necromancy out of the graveyard and back onto the battlefield. In turn, Necromancy's entry triggers its own resurrection effect, plucking the Archon right back out of the graveyard and strapping itself to it as an Aura—ready to begin the whole process anew for an endless supply of mana and triggers.