Masters of the Ancient Wisdom
The Masters of Wisdom are said to be enlightened beings living largely on the etheric plane of Earth. Starting in 1875 the Theosophists Helena Blavatsky, Henry Steel Olcott, and Alfred Percy Sinnett claimed to have met some of these great teachers in the remote areas of Tibet and India. Although these spiritual adepts have remained largely unknown in the West, they have long been referred to in esoteric writings as "The Brothers" (i.e., the Elder Brothers of the Human Race), "The Mahatmas", "The Lords of Compassion" and "The Masters of Wisdom". These "spiritually illumined men...are known historically, among others, as Hercules, Hermes, Rama, Mithra, Vyasa, Krishna, Confucius, Zoroaster, Shankaracharya, the Buddha, Christ, Mohammed." Helena Blavatsky was the one who re-introduced the New Testament Greek study of Theosophy or "Divine Wisdom" to the West and presented it not as a distinct religion, but a science. (Aspects of it came not merely from the 3rd Century Philaletheian philosophers, who had studied both sacred religious texts and yogic practices in India, but also from Neo-Platonists who belonged to diverse religions, and an Egyptian priest named Pot-Amun who lived during the Ptolemaic Dynasty.) Since its inception, the motto adopted by the Theosophical Society has been, "There is no religion higher than Truth." One of Theosophists' chief aims has always been to unite diverse people through a pursuit of ethics and irrefutable, underlying principles. In this manner, they focus not merely on fostering human development and freedom of thought but also promote peace. Two of the Masters of Wisdom, Kuthumi (K.H.) and Morya (M.), were said to have agreed to maintain a correspondence with two British Theosophists, Alfred P. Sinnett and A. O. Hume, from 1880 to 1885. The originals of these letters are currently being housed in the British Library in London and were published as the Mahatma Letters. Since Blavatsky's death, the writings of Alice A. Bailey, Helena Roerich, Manly P. Hall, Krishnamurti and Benjamin Creme have permitted previously esoteric and occult knowledge about spiritual development to grow more widely known, although a relatively small number of people recognize the source of these teachings as coming from the Masters of Wisdom. Nonetheless, the teachings are available to all those who might search for them as every single Master up unto Maitreya, the head of the Masters, is focussed upon uplifting Humanity. Overview

H.P. Blavatsky 
In the late 19th century, Helena Blavatsky and Henry Steel Olcott (the founder of the Theosophical Society), brought attention to secret initiatory knowledge they learnt from a group of enlightened yogis called "Mahatmas" or Masters of the Ancient Wisdom. These Masters were living in the Himalayas of remote India and Tibet:

Annie Besant and C.W. Leadbeater 
Annie Besant and Charles W. Leadbeater were colleagues of Helena Blavatsky and Henry Steel Olcott; they led the Theosophical Society of India. In The Masters and the Path (1925), Leadbeater underscores how every being is continuously evolving: there is a spiritual drive within each human being. He notes that over time a nation's history is ordinarily equated with the accomplishments of its greatest artists, scientists, philosophers, inventors, spiritual leaders, as well as enlightened politicians and philanthropists (even while the majority of such people operate so far beyond the realm of ordinary, consensual thinking and behaviour that they either remain unknown or are condemned while alive). Such individuals are not consumed by a desire to pursue comfort, power, or wealth. Rather they have been able to bring the control of their bodies, emotions, and mind under the direction of their soul (which is a mere fragment of the Monad, or spirit of God). As such, they are said to be approaching self-mastery. After undergoing a series of trials over lifetimes, those striving to mature spiritually shift their orientation towards life into a less and less personal direction, and thus grow less self-involved or subjective. Masters are those who have acquired the capacity to sustain heightened states of consciousness; they have evolved beyond the limits of the soul and function purely as monads. They are presented as beings full of wisdom and compassion, untouched by death and the limitations ordinarily associated with the body for their bodies require no food, defy age, can appear in different forms, and can be dematerialized through an act of will. While the Theosophists largely have focused on diverse writings emerging out of ancient "Egypt, Greece, India, Chaldea and Arabia" (including the great myths which hide within themselves the very Laws of Nature and the science of energies or the "Occult"),  Besant emphasizes that "the teaching can only be fruitful if it is lived." Alice Bailey and Benjamin Creme 
Alice Bailey and later Benjamin Creme asserted that there were 63 Masters of Wisdom who are actively involved in accelerating Humanity's evolution. (Bailey claimed the Master Djwal Khul to be the telepathic source of her books on esoteric philosophy, while Creme would never mention the Master whom he worked with by name). According to traditional Theosophists, the  Masters make up the Fifth Kingdom on Earth (that which is above the human, animal, vegetable and mineral kingdoms). The Masters also act as the Earth's planetary government, and are known as "the Hierarchy." As such, they serve as mediators between Humanity and Sanat Kumara, the Being Who ensouls this Planet. Their role is to transmit the Will of the Planetary Logos and thereby uplift and protect Humanity. In addition, the Masters of Wisdom are said to live in both etheric and physical bodies. Two-thirds of the Masters assigned to Humanity actually live on the physical plane, having chosen to sacrifice themselves by remaining behind to help Humanity. These Masters generally reside in the remote deserts and mountainous areas of the world from where they work directing certain energies to foster human progress and give birth to new civilizations, even while remaining for the most part unknown. (Theosophists attest that they work through their disciples, communicating telepathically). Like the earlier Theosophists who came before him, Creme was interested in the intersection of science, cosmology, psychology, politics and spirituality, as expressed here in his understanding about the origin of Humanity, its evolutionary journey, and the sacrificial nature of the soul:Nonetheless, while lecturing internationally Creme would stress that Humanity is at this time in history undergoing a great spiritual crisis: This is in part due to men's blind pursuit of market forces ― for all things, relationships and experiences are being commodified; for life, and war, itself, is considered a business. Over four decades, Creme emphasized how such a path was leading Humanity to self-destruction and that it was in part due to ordinary individuals' sense of separation, and thus complacency about others, other nations, and other life forms. He accounted for the turmoil also as a product of the ending of one astrological age, the Age of Pisces ― with its undue focus on the individual ― and the beginning of another, the Age of Aquarius, which will be reoriented towards group unity and synthesis. During the transition from one cosmic cycle to another, he underscored how there would be an influx of new, powerful energies, resulting in "fundamental, radical" changes in all areas of life. (In fact, this is what is referred to in the Bible as the "Apocalypse"). In order to restore a greater sense of Oneness, according to Creme, the Masters of Wisdom are returning to the everyday world, with their Head, Maitreya. They come as Humanity's elder brothers, mentors and guides, not as saviours. Maitreya, whose coming was predicted by Gautama Buddha, is said to be the Teacher of the World for the Age of Aquarius. His teachings may seem both simple and profound, familiar and new, intimate and practical. He is quoted as saying, "The problems of humanity are real but solvable. The solution lies within your grasp. Take your brother's need as the measure of your action and solve the problems of the world. There is no other course." By teaching the art of right relationship and self-realization, Maitreya and the Masters offer the hope to all of Humanity that, one day, every single one of us might achieve self-mastery. While Maitreya poses neither as a political nor religious leader, he is said to be "an educator in the broadest sense of the word, showing the way out of the present world crisis," by providing counsel about the nature of love, its immediacy and livingness. Both love and justice are what are now required for the healing of the World. In this way, one does not merely learn esoteric concepts from the Masters of Wisdom, but becomes engaged in a dynamic process in which one matures spiritually, growing more and more like them. Skeptical view
K. Paul Johnson hypothesizes in his book, The Masters Revealed: Madame Blavatsky and Myth of the Great White Lodge, that the Masters that Madame Blavatsky wrote about were merely idealizations of certain people she had met during her lifetime. Similarly, by studying period correspondence and a memoir, Richard Cloud conjectures that Blavatsky's meeting with the Kempten Rosicrucian adept Alois Mailander (1843-1905) served as the inspiration for her writings about the Master Morya. 