This unpopular group fills the heads of the young and vulnerable with obscure drivel about 'experiments' and 'rational explanations'. For example they insist that the tides are caused by invisible rays of force that emanate from the moon, rather than being the sea god Numen Mari breathing. They are the enemies of all gods (other than the god of low self-confidence, who does not believe in himself).
Their members have, however, gained some respect in the adventuring field, since their fanatical beliefs allow them to use ancient technology with less danger, to resist sorcery (unfortunately this includes useful magics as well as harmful ones), and to shake the self-confidence of demons and evil spirits; they have been known to convince ghosts that they do not exist.
It is rumoured that the Inventists posess a suit of clothing with the power to destroy magic. Its parts are said to include the Suspenders of Disbelief, and the Selfish Jeans.