Obligatory: the art here rocks!
I absolutely love the design for these retainers - it's simple (/complimentary), easy-to-read and parse, and feels useful and actionable. If my party ever got into the situation of taking on apprentices, I would absolutely deploy these retainers.
The only thing I would note: it would be useful to have a page number/reference for the Disciple's Hurl Magic ability.
Awesome job!