Cast Day of the Dragons by paying 7 life due to Demon of Fate's Design.
When Day of the Dragons enters the battlefield, its first ability and Cloudstone Curio trigger.
Resolve the Cloudstone Curio trigger, returning nothing to your hand from the battlefield.
Resolve the Day of the Dragons trigger, exiling all creatures you control and creating that many 5/5 Dragon creature tokens.
When the Dragon(s) enter the battlefield, Cloudstone Curio triggers that many times.
Resolve all but one Cloudstone Curio trigger, returning nothing to your hand from the battlefield.
Resolve the final Cloudstone Curio trigger, returning Day of the Dragons to your hand from the battlefield.
When Day of the Dragons leaves the battlefield, its second ability triggers, causing you to sacrifice all Dragons you control and return all cards exiled with Day of the Dragons to the battlefield.
When the creatures that were exiled by Day of the Dragons enter the battlefield, Cloudstone Curio and Verdant Sun's Avatar trigger that many times.
Resolve all Verdant Sun's Avatar triggers, causing you to gain life equal to the collective toughness of the creatures that entered the battlefield.
Resolve all Cloudstone Curio triggers, returning nothing to your hand from the battlefield.
Repeat.
With Enchanted Evening turning every permanent on the board into an enchantment, Demon of Fate's Design lets you cast Day of the Dragons for a mere 7 life instead of its normal mana cost. When Day of the Dragons enters, Cloudstone Curio lets you bounce it right back to your hand using the newly minted Dragon tokens as enablers. As the original creatures are returned from exile by Day of the Dragons leaving the battlefield, Verdant Sun's Avatar ensures you harvest a massive wave of lifegain, padding your life total to continuously fuel Demon of Fate's Design and repeat the entire loop indefinitely.