posted this as a review a while ago but it should be here too
HAZARD FUNCTION is the Tomb of Horrors of FIST - An instantly fun, iconic dungeon crawl, themed around being difficult, that's designed to teach you how to think when approaching the game, and to create fun stories about the characters' well-earned triumphs and gruesome failures.
My advice to referees would be to embrace the "trial-by-fire" setting of the Crucible; it will be more interesting if you treat each room as its own mini-mission, as opposed to a series of increasingly difficult killboxes (but that way is fun too).