Can you elaborate on the 4th degree of the ancient and accepted Scottish rite, the secret master?

A key made of ivory is presented to the candidate in the 4th degree, Secret Master, as the Scottish Rite's official site notes.

Historically, commentators such as Chemin Dupontes criticized earlier Scottish rituals of the degree for being excessively filled with Hermetic philosophy, though later revisions focused more directly on the importance of truth as the central dogma 1. The symbolism relies heavily on the development of the number three 1. Bodies working the degree were designated as Chapters, governed by a Most Excellent Chief Prince and Wardens styled as Excellent—officers who in earlier rituals represented Moses, Aaron, and Eleazar before those specific personations were removed 1. The degree's apron is bordered in red and white, and its jewel features an equilateral triangle enclosing a heart 1.

In the broader Hermetic philosophy associated with the Scottish Masters, five symbolic operations or rules are delineated 2. These draw upon alchemical allegories—such as extracting sulphur from pure gold and employing celestial salt—and connect each stage to sacred emblems, including the Ark, the Tower of Babel, the Cubical Stone, and the Flaming Star, to represent the purification and elevation of the human spirit 2.