This skill allows you to handle more ghosts. Basically this means you are privileged to know the customs of the ghosts and the borders not to cross. It also helps you to organize the ghosts in hierarchial way, giving them sense of self-control. The skill is automatically in effect.
The research on this skill was started by Samuel de Montfort, and mastered by one of his humble followers. The legend has that part of this mastering process rendered the follower into a nameless ghost, but with her research left, it was easy to limit the amount of affinity allowed to the members of the guild. The name of the follower might still be found in the guild library, but when consulted in a seance, she wanted to stay anonymous. Her wish is to be treated with utmost respect - the ghost world accepted her as one of their own, and breaking this wish might result in uprising.