Or Blaise, Bleys or Blaze: Called »Merlin's master« in much of the Matter of Britain, he is, however, no sorceror; it is a misconception to think of him as Merlin's teacher in the Art, which the latter has by nature and the grace of God. Rather, Bloyse is a monk, a »master« in the same sense as Meister Eckhart — one practiced in the art of writing; a clerk. He baptizes the cambion Merlin at birth, cleansing his soul of evil — although the efficacy of this ministration varies; the Vulgate Cycle (which, tellingly, also denies his baptism) claims that Merlin never did a good deed, and for the most part, he retains a Cassandran aspect, prophesying mostly doom to men unwilling to listen. Subsequently Bloyse chronicles the rise and fall of Camelot and the acts of the Knights of the Round Table.

Bloyse is created with Merlin by inveterate liar Geoffrey of Monmouth, in the Vita Merlini; after this he is most prominent in the Vulgate Cycle and the Prose Merlin. In Malory, Bloyse remains a phantom; he appears only once, in Book I, when it is mentioned that Merlin visits him repeatedly to recount the events of Arthur's reign, to see them set in writing. Since Merlin exits the tale early in Book IV (of 21), it is difficult to understand how the rest is supposed to have come down to us; but there are greater problems in the Morte.