Cast the Dinosaur in your hand by paying its mana cost. It will enter with a coin counter due to Blue.
Activate Shilgengar by sacrificing the Dinosaur.
When the Dinosaur dies, Athreos's second ability triggers, returning the Dinosaur from your graveyard to the battlefield. It will enter with a coin counter due to Blue.
Resolve the Shilgengar ability.
Repeat from step 2.
This engine leverages the synergy between Blue, Loyal Raptor and Athreos, Shroud-Veiled to constantly recycle your creatures while generating an endless supply of Shilgengar, Sire of Famine's Blood tokens. Thanks to Blue, Loyal Raptor's passive ability, your incoming dinosaurs automatically inherit the coin counter placed by Athreos, Shroud-Veiled, ensuring that whenever you sacrifice them to Shilgengar, Sire of Famine, Athreos immediately triggers to return them straight back to the battlefield. This creates a self-sustaining loop that infinitely triggers sacrifice, death, and entry effects while fueling the graveyard recursion of Shilgengar, Sire of Famine.