For a Master, I have some idea's but I'll have to iron them out.
But it is going to be a Greek Mage by the name of Leviticus Masters.
Fate Academy is about a mage school, where the first year students hold a Fate/Apocrypha type tournament, with a huge cast of Servants, being whittled down to 21 and then to 7 and then to 1.
So like a huge scale grail war set in a edgier Harry Potter type boarding school.