The Horroroso had been defeated by Team Legend and that Quetzalcoatl's Portal has been sealed by the Mystic Bomb, the entire city of Puebla rejoiced. Leo was praised by Peter, who called him a weirdo, but they're weirdo and the town thanked him. Marcella even kissed him on the cheek as a sign of thanks. However, their celebration was cut short.
Only moments after, the black mass of Quetzalcoatl attacked, wiping away buildings from the plane of existence. Though Marcella and Leo ran to safety, their attempts were in vain. The monastery was consumed and so was Marcella. Downtrotted by the events, Leo realized then and there that he could ignore his destiny no more and started the fight against Quetzalcoatl.
After the attack, the entirety of Puebla was gone, only leaving the plots of land where the buildings were built upon. Leo only managed to survive thanks to his friends flying the Airship to his rescue. Utterly devastated at the lost of his home, his friends and his family, Leo takes a stand to take his destiny far more seriously.
Leo mentioned what happened to Thomas Decatur, who took symphony on Leo and wished to help him.
When in the Dream World, Leo has nightmares regarding what he perceives Puebla to be like under Quetzalcoatl's control. His predictions are eerily similar to what the town is actually like.
The guilt over losing Puebla has driven Leo to the point where he nearly sacrifices his friends in order to further his goals. However, Leo comes around and realizes that if he does so, he'd be no better than the monsters he's fighting.
Team Legend travel to Puebla after it's been consigned to Quetzalcoatl's realm. Afterwards, Marcella joins Team Legend as a way to save Puebla.
Marcella remarks that being in Quetzalcoatl's dimension has made her tough, tough enough to deal with Phineas Blackpulp.
Marcella mentions that losing Puebla is one of her biggest regrets.
The Conquering of Puebla affected all of Team Legend and lead to significant character development for them. However, by far Leo and Marcella were affected by the incident the most. The incident kicked off Leo's dormant bravery and adventurous heart, that he lost over the years, while it ignited a heroic spirit within Marcella. Indirectly, the event also affected Prince Akihito greatly as well, as Marcella telling him of what happened, and the bravery of Friar Godofredo convinced Akihito to step up and be the ruler he should've been earlier.