Helena Petrovna Blavatsky was a Russian-born mystic and traveler who wrote the epic books Isis Unveiled in 1877 and The Secret Doctrine in 1888 (among other articles and smaller books). She also co-founded the Theosophical Society in New York City in 1875. Here is a 1991 Russian TV drama/documentary that the Cardiff Theosophical Society in Wales recommends as a good introduction to Blavatsky.
I’ve been reading a few books by Annie Besant, and was very pleased to find this documentary on youtube. Watch here or save the mp4 version. Besant was an important figure in the mystical Theosophy movement of the late 1800s/early 1900s, which believes all humanity (all existence, even) is one family, and that there is an underlying Truth to all the major world religions and mystic traditions.
I did not know before watching this video that the theosophists “discovered” Jiddu Krishnamurti, and Annie Besant trained him to be a “gentleman” and spiritual teacher (many saw him as a messiah figure; he officially separated from the Theosophical Society in 1929). I also did not know that Annie Besant was an activist for social reform, workers’ rights and women’s rights, creating scandal with her endorsement of birth control. She is probably best known for her explorations into spirituality and religion, and her campaign for democratic independence in India.