Malachy may also be the author of a treatise, De veneno, on the seven deadly sins, published in Paris in 1518 and alternatively attributed to Robert Grosseteste. It is stated as having been written "for the instruction of simple men who have to teach the people". The edition stated that he was a Franciscan preacher who was alive in 1300, "a doctor of theology, a strenuous expounder of the scriptures and a most zealous rebuker of vices." Apparently he also wrote a book of sermons, now lost. John Bale recorded that he was well received in Ireland, esteemed at Oxford, and preached before Edward II.