Astral Dragon enters the battlefield, triggering itself and Miirym.
Resolve the Astral Dragon trigger, creating four token copies of Primal Vigor that are 3/3 Dragons in addition to their other types.
Resolve the Miirym trigger, creating a total of 32 Astral Dragon tokens.
The Astral Dragon tokens enter the battlefield, creating an extremely large number of Primal Vigor tokens that are 3/3 Dragons in addition to their other types.