Double Agent
Grivon entered the Grey Marsh that same day along with his crew and directly went after the main branch of the organization.
He and his team wore navy blue cloaks fully covering their bodies. They even used some crystal eye masks that mask their eyes. They are extremely powerful. His team has extremely high-level cultivators and every one of them could be considered overkill.
He has a necromancer who collected souls and got the information. He learned who the head of the organization is passing the information to and where they are keeping the mutated hatchlings and the locations of the contained environments for the fully grown beasts.
He went with the team and started hunting until the next day as he collected the beasts and specter collected souls.