From Discworld & Terry Pratchett Wiki
|Books||Carpe Jugulum, The Science of Discworld IV: Judgment Day|
|Cameos||Unseen Academicals, Snuff|
The Quite Reverend Mightily-Praiseworthy-Are-Ye-Who-Exalteth-Om Oats: an Omnian missionary priest who found himself entangled in a war with Vampires from Überwald who planned to take over Lancre. He came from Ohulan when he was asked to fill in for the injured Brother Perdore at the naming ceremony for Princess Esmerelda Margaret Note Spelling of Lancre (so called because Nanny Ogg made him so nervous that he read the instruction as part of the name). He was then of heroic assistance to Granny Weatherwax in the fight to evict the Count de Magpyr and his family, whom King Verence had invited for the ceremony. Oats was similar to Agnes Nitt in that he possessed a rifted personality - his penchant for asking questions contradicted his training to accept things on faith. This trait made him mostly immune to the vampyres' mind-control techniques, a feat that even the four Lancre witches (excepting Perdita) couldn't perform. Rev. Oats is an unusually sympathetic churchman for the Discworld: not hypocritical, a true believer, but also prepared to burn his beloved Book of Om in the service of mankind.
Mightily Oats has grown in faith and might. He appears in Unseen Academicals as an early protector and mentor of the otherwise loathed and persecuted Mr Nutt. It seems as though his faith, forged in the fires, has hardened into steel. He preaches forgiveness, and Forgiveness is the name of the double-headed battleaxe that he carries with him through the fearful places of the world: faith is REAL to Pastor Oats. Nutt was rescued by Oats, and now he will travel back with him to the Evil Empire to rescue what may be left of his brethren.
Pastor Oats is mentioned in I Shall Wear Midnight by an Omnian priest (Pastor Egg) who tells Tiffany Aching that in his Testament from the Mountains Oats said that witches embody the best ideals of Brutha the prophet (the main character from Small Gods).
He reappears in The Science of Discworld IV: Judgment Day to make a reasoned case at the trial hearing concerning ownership of the Roundworld, and is much altered from his appearance in Carpe Jugulum. It is clear that Vetinari holds him in high esteem, and his case swings the day against the Church of the Latter-Day Omnians.
His name has a curious echo of Titus Oates, the seventeenth-century anti-Catholic rabble-rouser and perjurer. If intentional, this must be to highlight a contrast; Oates was voted the third-worst Briton of the millennium in a recent poll.
It should be noted that "May you do so mightily" is a response to a request to relief yourself in some African tribes (obviously a translation) according to Nigel Ree's All Gong and No Dinner. Maybe Mightily Oats means to get your oats mightily then?