Short answers, pulled from the story.
Dungeons & Dragons Master Rules covers character levels 26 through 36. It was the fourth set in Frank Mentzer's five-part series, following the Basic, Expert, and Companion rules sets.
The books in the Dungeons & Dragons Master Rules set were written by Frank Mentzer and edited by Barbara Green Deer, Anne C. Gray, and Mike Breault. Larry Elmore painted the cover artwork, and interior illustrations were provided by Jeff Easley and Roger Raupp.
Weapons Mastery is a system introduced in the Master Player's Book that tracks a character's progression with a weapon from Novice to Grand Master. A full table lists every weapon in the D&D game, including damage values at each Mastery level, defensive uses, costs, weights, and special effects.
The mystic is a character class introduced in the Master Player's Book, described as an empty-hand warrior. It was one of several additions the set made to the existing character options in Dungeons & Dragons.
Dungeons & Dragons Master Rules was first published in 1985 as an expansion to the Basic Set. It was part of a series of five boxed sets developed by Frank Mentzer between 1983 and 1985.
Paul Cockburn reviewed Dungeons & Dragons Master Rules in issue 73 of White Dwarf magazine, dated January 1986, rating it 8 out of 10. Cockburn described it as an intelligent, subtle, and interesting extension to the game.