You have a transforming double faced creature or enchantment card in hand.
({7} magic symbol) ({U} magic symbol) , plus enough mana to cast the double-faced creature or enchantment available.
Steps
Activate Yenna by paying ({2} magic symbol) and tapping it, creating two token copies of Doubling Season.
Cast Infinite Reflection by paying ({5} magic symbol) ({U} magic symbol) , attaching it to Inventive Iteration.
When Infinite Reflection enters the battlefield, it triggers, causing each nontoken creature you control to become a copy of Inventive Iteration.
Cast any transforming double-faced creature or enchantment card by paying its mana cost, causing it to enter the battlefield as a copy of Inventive Iteration with four chapter counters due to Infinite Reflection and the Doubling Season tokens.
The creature or enchantment's first, second and third chapter abilities trigger.
Resolve the first and second triggers, returning up to one creature or planeswalker to its owner's hand, and then either returning an artifact card from your graveyard to your hand or causing you to draw a card.
Resolve the third trigger, exiling the creature or enchantment, and returning it to the battlefield transformed as a copy of Inventive Iteration with four chapter counters due to Infinite Reflection and the Doubling Season tokens.
Repeat from step 5.
When your library is down to one card remaining, use the creature's first trigger to return the original Inventive Iteration to your hand, thus ending the loop.
Results
Infinite card draw.
Infinite draw triggers.
Near-infinite ETB.
Near-infinite LTB.
Return all artifact cards from your graveyard to your hand.
Return any number of creatures and/or planeswalkers to their owner's hand.