It was clear that Zhou Li wasn't planning on taking his entire Lizi Class to the Hundred Flowers Banquet; that would be no different than taking a dump on the Emperor's head.
So, he only planned to bring a few people.
Lord Wan Sui was a given. She was incredibly strong, able to defeat Sixth Realm Spirit Qi Masters easily and even hold her own against Seventh Realm Spirit Qi Masters. Plus, her soul-eating physique allowed her to command the "Spirits of the Five Elements," significantly restraining those who used Five Elements Taoist Arts or Five Elements Spirit Qi. In situations where Zhou Li wasn't unleashing his full firepower, Lord Wan Sui was undeniably the top combatant in Lizi Class.