Who is Miles Teg from Heretics of Dune and what is their importance?

Miles Teg is a brilliant Supreme Bashar retired from commanding the Bene Gesserit military forces, Teg reluctantly returns to service on the planet Gammu to train and protect the latest Duncan Idaho ghola, placing his most trusted aide, Patrin, in immediate charge. The son of Reverend Mother Janet Roxbrough, who has Fish Speaker blood, and a CHOAM minor functionary, Loschy Teg, Teg inherits the house on Lernaeus when Roxbrough dies. Suspecting Mentat abilities, Roxbrough sends her son to Chapter House Planet for training beyond the things she teaches him illicitly a la Lady Jessica.