Elementaries refers to various entities that we create through the misuse of our sexual energy. Examples include incubi, succubi, basilisks, etc. They abide in the fifth dimension where they pressure our mind with thoughts, desires, imaginations, and dreams to give them more energy, especially through masturbation, sexual fantasy, etc. Do not confuse with elementals, which are innocent creatures of nature.
"...when Cain had killed Abel, Adam separated from his wife and cohabitated with two female elementals, and from his intercourse with them was begotten a great and numerous progeny of demons and elementaries who at night time appear in attractive forms and thus give rise to offspring like unto themselves. In scripture, they are termed 'the plagues of the children of men... Woe unto those who are ignorant and therefore unable to avert and ward off the influence of these defiling elemental beings that swarm in their myriads throughout the world. If it were permitted to behold them, we should be amazed and confounded and wonder how the world could continue to exist. Observe that Naamah being the exciter of human concupiscence and carnality, it is obligatory on everyone to practice and perform acts and rites of purification, so that he may become and preserve himself pure and undefiled." —Zohar
“Eliphas Levi applies equally the term "elementary" to earth-bound human spirits and to the creatures of the elements. This carelessness on his part is due to the fact that as the human elementaries are considered by the Kabalists as having irretrievably lost every chance of immortality, they therefore, after a certain period of time, become no better than the elementals who never had any soul at all. To disentangle the subject, I have, in my Isis Unveiled, shown that the former should alone be called "elementaries," and the latter "elementals" (Before the Veil, Vol. I, pp. xxix-xxx)... Having never studied the Kabalist writers, it becomes evident to me that [many] confound the "elementaries" — disembodied, vicious, and earth-bound, yet human spirits, with the "elementals," or nature-spirits.” —Blavatsky
"...whoever wants to have that which normally is called soul will have to disintegrate the undesirable psychic aggregates that we carry within, namely: anger, greed, lust, envy, pride, laziness, gluttony, etc... Obviously, those crimes are the representation of our defects, which in Tibet are named psychic aggregates. Those aggregates are the very same “elementaries” that are mentioned by different occultist organizations. They are the living representation of our errors." —Samael Aun Weor, About the Soul
Learn more: Zohar: And the Darkness Was Called Lilith
"Certain wicked and dangerous results may be obtained through the mesmeric powers of a so-called sorcerer, who misuses his potential fluid; or again they may be achieved through an easy access of malicious tricky "spirits" (so much the worse if human) to the atmosphere surrounding a medium. How many thousands of such irresponsible innocent victims have met infamous deaths through the tricks of those elementaries!" —Blavatksy, Isis Unveiled