Master Serepis, mentioned in Theosophy and other occult philosophy, is one of the Masters of the Great White Lodge, the secret brotherhood that supervises the spiritual evolution of the earth. He is the chohan of chief adept of the Fourth or Green Ray, the ray of harmony, beauty, nature, and the arts.
Master Seperis seemed to be the head or supervisor of the Great White Lodge or the Brotherhood of Luxor as otherwise named. These Masters, seven in number, to Madame Blavatsky were not entities from the cosmos plane of existence such as John King, but actual men with headquarters somewhere in Egypt.
Greer, John Michael. The New Encyclopedia of the Occult. St. Paul, MN, Llewellyn Worldwide. p. 430
Meade, Marion, Madame Blavatsky: The Woman Behind the Myth, New York, G. P. Putman’s Sons, 1980. pp. 138-139