Learn English – A single word for a person who suffers great loss

In some professional organizations, the word "Journeyman" is used for someone who has passed their apprenticeship and able to complete work on their own, but are not necessarily masters yet.

EDIT: If you are seeking a skill level reference for learning material. This seems to be a standard:

For Beginner [programmers, developers, carpenters, chefs]
For Intermediate [programmers, developers, carpenters, chefs]
For Advanced [programmers, developers, carpenters, chefs]

You are asking for a word to replace "intermediate", but the more I think about it "intermediate" may actually be the word you need.

How about disciple?

disciple: one who accepts and assists in spreading the doctrines of another; a convinced adherent of a school or individual [Merriam-Webster]

disciple: person who is a pupil or an adherent of the doctrines of another; follower [Dictionary.com]

disciple: one who embraces and assists in spreading the teachings of another [The Free Dictionary]

disciple: a person who believes in the ideas and principles of someone famous and tries to live the way that person does or did [Cambridge]

disciple: a follower or student of a teacher, leader, or philosopher [Oxford]

I can easily imagine using disciple in a video game. I like it better than sidekick. :-)