At the very beginning of Leo I's pontificate, in the years 444-447, Turribius, the bishop of Astorga in León, sent to Rome a memorandum warning that Priscillianism was by no means dead, reporting that it numbered even bishops among its supporters, and asking the aid of the Roman See.
Paavst Leo I pontifikaadi päris alguses aastatel 444–447 saatis Astorga piiskop Turribius Leónist Rooma memorandumi, hoiatades, et priscilliaanlus ei olnud kaugeltki surnud, teatades, et tema arvukate toetajate hulgas oli isegi piiskoppe, ja küsides Pühalt Toolilt abi.