I am concerned that this companion is less bellicose than might fit the needs of an intended hoplite character. That said it does seem rather authentically medieval to me, and I like that.
What would you say to making this companion a member of the Priory that is on Inchmore Island and therefore a local, who has taken an interest in the Covenant that is now founded on the island?
Perhaps he thinks these Magi need spiritual guidance, whether they are his designated flock or not?