Master
In most cases, a "master" in the Bible refers to truth. That can vary according to the person being called master -- Egyptian masters respresent factual, worldly knowledge; when the Lord is referred to as master it means Divine Truth itself. The term does vary according to context. If the things directed by the "master" represent knowledge and ideas, the master will represent desires for good, since desires for good are the things that inspire true thinking.
Fat and river of pleasures
In Psalm 36:8, the 'fat' and 'the fountain of life' stand for the celestial, which consists in love, and the 'river of delights' and 'light' stand for the spiritual, which consists in faith deriving from love. (Arcana Coelestia 353)