Activate Shilgengar by sacrificing Glasspool Mimic.
When Glasspool Mimic dies, its last ability from Cavalier of Night triggers, returning itself from your graveyard to the battlefield as a copy of Cavalier of Night.
When Glasspool Mimic enters the battlefield, its first triggered ability from Cavalier of Night triggers; choose not to sacrifice a creature.
Resolve the Shilgengar ability from step 1.
Repeat.
This looping engine relies on the interplay between Shilgengar, Sire of Famine and a cleverly disguised copy. By activating Shilgengar to sacrifice Glasspool Mimic—which is currently copying Cavalier of Night—you trigger the underlying Cavalier's death ability to instantly resurrect the Mimic right back to the battlefield as another copy of the Cavalier. This endless cycle of sacrifice and rebirth churns out infinite Blood tokens and death triggers without ever needing to break a sweat.