This dazzling loop begins the moment you cast Astral Dragon, whose entry triggers both its own token-making ability and Flameshadow Conjuring's red mana-payment trigger. By targeting Primal Vigor with the Dragon's ability, its replacement effect causes an exponential explosion of token doublers, turning four copies into a multiplier-laden battlefield. When Flameshadow Conjuring then resolves and you pay the required red mana, it creates a massive wave of Astral Dragon tokens that cascades into an unfathomable number of repeating triggers and near-infinite creatures.