The title Magus (5th. degree) is reserved for the High Priest. Here is a description from the affiliation page on the Church of Satan
"Priesthood of Mendes
These are the individuals who act as spokespersons for the philosophy of the Church of Satan
, which include the titles of “Priest”/“Priestess,” “Magister”/“Magistra,” “Magus”/“Maga.” Members of the Priesthood make up the Council of Nine, which is the ruling body of the organization, responsible to the High Priest/Priestess. The Order of the Trapezoid consists of the individuals who assist in the administration of the Church of Satan
. Members of our Priesthood are people of accomplishment in the real world—they have mastered skills and have won peer recognition, which is how they have attained their position—“as above, so below.” They are “movers and shakers” who are the core of our movement. While expected to be experts in communicating our philosophy, they are not required to speak on our behalf and they may even choose to keep their affiliation and rank secret, in order to better serve their personal goals, as well as those of our organization. Thus, you may (even as a member), encounter members of our Priesthood and never know it.
Membership in the Priesthood is by invitation only. The old truism “If you have to ask, you can’t afford it” is certainly highly pertinent to our Priesthood. Words to the wise: Do not ask “How do I become a Priest?”