The House of Sand is but a rumor to most, but there are those that listen to the streets of the great cities telling of an organization of master assassins that has it’s fingers in almost every criminal organization.
Actually a real-world fungus, just heard about it. A fungus that tastes well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick, pains, vomiting, all the fancy stuff. Was really used to cure alcoholism. May be a joke or to make sure the heroes spend their time focused on the mission.