This ingenious loop relies on turning your entire board into enchantments using Secret Arcade // Dusty Parlor, transforming every single permanent spell and nonland permanent you control into an enchantment in addition to its other types. Because of this static ability, when you cast Archon of Sun's Grace, it enters the battlefield as an enchantment, triggering its own constellation ability to create a 2/2 white Pegasus token. Since that newly created token is *also* an enchantment thanks to Secret Arcade // Dusty Parlor, it immediately triggers Archon of Sun's Grace to make another token, creating a mandatory, unstoppable loop of entering-the-battlefield triggers that forces a draw if no player can interrupt it.