Fantasy/Occultism nerd here. I hope my answer is thorough enough, I have recommendations for further reading if anyone is interested. Occultism/Esoteric philosophy is a tangled field so I'm not going to bomb my response with a million links nor dig too far into symbolism or correspondences (tarot, elements, numbers, etc) but will provide a decent rundown of two specific fields of Esoteric thought, both of which are descended from Kabbalah and Hermeticism (which have had a huge influence on Fantasy media all their own) and the major figures in them:

A. Enochian Magic is a system primarily focused on communicating w supernatural entities and gaining hidden (occult) knowledge, pioneered in the 16th Century by Elizabeth I's court astrologer/adviser John Dee and his assistant Edward Kelley. Dee and Enochian Magic pretty much give us the modern conception of a wizard: long beard, tall dark tower lab, dusty ancient tomes, a court adviser moving and manipulating from the shadows. Dee himself has been the basis for many fictional wizards over the years, possibly even Shakespeare's Prospero. It's relevant to note here that the actual magical practice, which i get into below, contains elements which have found their way into what we'd recognize as both the Wizard and Warlock Dungeons and Dragons (and similar) classes as opposed to a more folklore type character like, say, Gandalf.

Dee's philosophy defined and combined many older practices, and the magical system itself deals in and codifies many of the tropes you may be familiar with from the modern Fantasy genre: magical seals and circles (either drawn/painted or projected ala Doctor Strange, the Hellsing manga/anime, etc*),* bargaining with and commanding elemental spirits, making pacts, scrying, far seeing, obtaining secret information on rivals and hidden treasure, wizard's staffs, wands, etc. There is also the concept of the Aethyr (similar to the Kabbalistic Sephera) which are various levels of existence which can be visited using Astral Projection (dimensions, worlds, planes, etc) or drawn upon to manifest specific powers (warrens in the Malazan series, channeling in Wheel of Time).

B. The Hermetic Order of the Golden Dawn was an occult secret society which existed for a little less than 20 years at the turn of the 20th Century. It's philosophy is roughly descended from Dee and Enochian Magic, but the Order's ritual practices and history have been an influence all their own. The Golden Dawn has been the basis for many fictional secret societies and sects since its inception (some of which were invented by its more illustrious members). Two examples which spring immediately to mind are 2009's Sherlock Holmes and the book/series Lovecraft Country. Again, many now classic fantasy tropes were a part of their practices and compiled from older traditions: hooded robes, various degrees based on the Freemason system of initiation, magical pseudonyms in dead tongues, members drawn from the influential and artistic elements of society (Yeats, Stoker, Blackwood, Doyle), secrecy, magical skirmishes between rival sects, etc.

The Golden Dawn is where Aleister Crowley, the most influential occultist of the 20th century, got his start. Crowley, like Dee, has become an archetype to himself: the rebel, the fallen apprentice, the modern-day evil sorcerer. Starting in his own lifetime, Crowley inspired many fantasy/weird fiction villains, starting with the Oliver Haddo character in W. Somerset Maugham's The Magician and continuing to the present day in Grant Morrison and Alan Moore comics, various Neil Gaiman works in comic, prose, and television, the shows Supernatural and Pennyworth, and many others.

These are the two big veins of magical inspiration on fantasy fiction that sprang to my mind but this is by no means an exhaustive write up. Part of the appeal of these two, imo, is they both are very much conglomerations of what was going on in Western esoteric thought at the time. Both are hugely influential but also hugely influenced by what had come before. Enochian Magic, for instance, has much in common with the older Abramelin Workings, which in turn were studied by Eliphas Levi who's writings were a huge influence on the the Golden Dawn, which then leads into Crowley spinning off on his own with Thelema and the OTO which then leads into modern Wicca (via Gerald Gardner and Scientology via Jack Parsons. The point I'm trying to make, I suppose, is a lot of the influence of the Golden Dawn and Enochian Magic comes from exposing creators to all the systems associated with them. They're a good starting point, in other words.

As I said at the top, please let me know if you'd like any book/essay/primary source recs on any of these points, I've got oodles. Also you may think of posting this same question to r/occult, its a pretty open and friendly community :)