You may have flashbacks of edgy goth teens claiming to be these while carrying around fake blood in wine glasses at the costume party when you hear this term, but it's not as cool--or edgy--as it sounds (and I would have used an alternative if I could have come up with a decent one). An energy vampire is, quite literally, somebody who is able to draw/drain energy (psychic, magickal, and/or emotional) from an artifact, entity, magician, etcetera. It's not really as difficult or as insidous as it sounds, it's literally just "charging" in reverse (see this article for the full rundown on artifacts and charging).
Do also note this term has been co-opted to generally mean "somebody who's, like, so totally draining to be around" and, at least for what we're using the term to mean, that... doesn't really apply. If somebody is being a fuckwad specifically to get another magician agitated enough to drop their guard so they can then attempt to grab a hold of them and drain a bunch of their aura energy, maybe. But just being a fuckwad who's draining to be around isn't vampirism. It's called being a fuckwad.
Ahem, moving on. It is typically possible for high level magicians who train in energy vampirism to be able to drain energy, even dangerous amounts, from other living things (including non-magicians), but to do so without permission is what most consider to be "a dick move" (and genuinely quite pointless--there's not enough relevant frequency energy to be drained from non-magicians/non-psychics anyway). It's also possible through various rituals (many of which are too NSFW to go on this site) to create essentially a feedback loop with another powerful magician that results in both parties reaching an over-charged state through mutual energy vampirism, as impossible as that sounds (it's also possible to make feedback loops/complex energy flow structures that don't basically create energy from nothing but are still helpful and don't require such methods--see the last paragraph of this article). Since humans and artifacts generally can't desynchronize from their auras/etheric bodies/etcetera (astral projection notwithstanding), draining usually requires physical touch, or being incredibly close to the person or object to be drained from. There's one exception, ambient recharging, which we'll go over later.
While it seems to be impossible to use so much aura energy that one "loses their aura" or dies, it's definitely a finite resource, so draining energy from SOMEWHERE is basically a requirement as one continues along their magickal journey and starts doing more complex, taxing, and energy intensive rituals and techniques. Some of my offense aura techniques for exorcisms, for instance, drain my entire reserves in not much more than a minute of staying activated. It is possible to learn to destroy evil liminal creatures, however, and to absorb their energy as your own, which can help immensely after a draining battle (I'll have to write an "oddity" feature about one such showdown from a few months ago soon).
Oh, and to clarify--the aura does naturally restore itself over time, but it's a slow(ish) process. Sometimes it's needed to recharge even without intentionally using up aura energy--I had the section of my aura overlapping my left index finger taking the form of my favorite and most capable local spirit, and lost a huge chunk of the aura--with a surprising amount of stinging physical pain--without even realizing I was getting into a fight (read this oddity feature for that full story). Even with as relatively little of my aura/energy as I lost, it took about 24 hours to fully regain it.
Oddly, I wasn't able to simply extend the rest of my energy towards that spot, nor to reform the local spirit, until the particular energy that been used up had "regrown." It seems, then, that there's something slightly different about aura energy that is "structured" into the actual shape of the etheric body (required to be present at all times, and impossible to manipulate like a forcefield like the rest of the aura, it seems) and/or made into a local spirit, and energy that is simply bound to the etheric body and kept at its frequency (the extendable and manipulable "aura," if you will). Even the local spirit didn't REMOVE that section of my etheric double while in use, it basically... performed an OBE from the etheric body, where it was able to interact then with other, non-local liminal entities. I assume this is possible due to the silver cord concept that binds the etheric double to the physical body it is currently inhabiting, but I've only experienced such an attack once thus far and don't intend to put myself in a situation where it can happen easily again. Regardless, rest assured that any aura energy that is used up or drained, and even any etheric-double-forming aura energy that is destroyed in an attack, is restored eventually. So too can spirits be reformed if they are left bound and the portion of the etheric double they inhabited given time to heal.
On the other hand, it is also possible to go overboard and charge TOO MUCH. This may sound like a silly concept, but it's quite real and quite unpleasant. One's total max energy capacity, as well as how much energy their techniques/magick/local spirits utilize, scale higher and higher as one grows in power with training and experience, but whatever that current "cap" is, it will be possible to exceed it. Doing so sends the third eye into absolute hyperdrive and will function as a buff to power/extrasensory abilities, but the side effect is similar to being far too caffeinated and facing a caffeine crash at the same time. All metaphysical stimulation will seem absolutely overwhelming, one's heart will race, and one will become incredibly restless, their aura "twitchy," and reaching the trance state--let alone falling asleep--will be essentially impossible.
In such situations, it is possible to charge an artifact (or, if powerful/overcharged enough, to create a new artifact by charging a regular object) to open the metaphorical pressure valve a bit and release enough to get one back to a healthy baseline at their maximum comfortable capacity. All steps of this process become easier with training, and don't worry--it is difficult to overcharge by accident, and very rare for it to happen at all. It only occurs when draining from an insanely powerful magician, entity, or artifact (or after absorbing a malicious spirit or entity of satisfactory power--that's a lot of energy to force into one's aura systems, even when it's shredded beyond having any unique signature or sentience). Like being drained of aura energy, I do not believe overcharging can kill somebody... it's just not incredibly pleasant.
It's easy to view energy vampirism as a dark/violent/offensive technique and charging as a healing/neutral technique, but that's a bit short-sighted. For one thing, sometimes energy vampirism is actually an assist technique--I've had to physically tear parasitic liminal creatures from other magicians before to save them from attacks, by basically just touching them, draining just that frequency, shredding it up as I absorbed it and then consuming and converting the remaining "raw' energy. And for another thing, it's very easy to ethically and morally source one's energy. Draining from artifacts is a very easy way, and it should be trivial to locate artifacts if one is at the point where they require/use up enough power to have to seek a recharge.
Training to hone one's sensitivity in energy/aura scanning will also open up a much easier option--ambient recharging. In areas full of powerful residual emotional/magickal/energy in objects, artifacts, haunted objects, etcetera, it is possible to drain from the very air around you to recharge one's self, as there is such a powerful "fog" of energy surrounding. And, in a situation where it's possible for such a "fog" or "haze" to form, there's too much energy constantly seeping out of artifacts for you to put a dent in that residual ghostly aura... so you may drain to your heart's/aura's content, guilt-free. Antique malls are often excellent locations for this, due to the sheer amount of ancient and haunted objects in most. Locations with strong consistent emotional "states" are also good candidates for this--arcades, for instance, have years and even decades of mostly positive energy in every machine, making an excellent ambient aura haze.
It is also, of course, possible to buy artifacts to drain at home... and it's basically impossible to fully drain an artifact's aura (plus they tend to regenerate over time somehow, perhaps in a phenomena related to the creation of homunculi). You can also, in most places, drain from artifacts without buying anything. If the residual energy at an antique mall isn't enough, for instance, or you can't quite sense and draw from the haze yet, or need a faster charge... whatever the case, you can just go around the antique mall instead and drain from artifacts. Nobody's going to tell you not to pick something up to look at it unless it's in a display case or something, and it doesn't take long to get a nice hit off an artifact, especially really cursed or haunted ones. Just make sure you don't accidentally agitate an entity that will attack, and you'll be gucci (if you can't distinguish what's actually possessed or not, maybe stick to other methods).
Finally, back to the whole "energy vampirism isn't inherently bad and charging isn't inherently good" thing... it's also possible to use charging offensively. A skilled/powerful enough enemy magician or entity could overcharge you, charge you specifically with a negative emotion or frequency or what have you, weaken and attack your own frequency (and therefore aura and, potentially in dire enough circumstances, etheric body) by pumping you full of their own to override it. In most aspects of occultism, and aura magick in particular, there are very few things that are inherently "bad" OR "good"...most techniques can be done ethically/assisting others OR done unethically/harming others.
So, to conclude... "energy vampirism," as cringe as the term has come to be seen, is a real thing... but most of the stigma associated with it is unwarranted. It's a crucial technique, alongside charging, and is but one side of the energy/aura manipulation coin, if you will. The two techniques can also be used in synch to create feedback loops or more complex flows of energy--it is entirely possible, for instance, for a skilled aura magician to drain a powerful artifact while simultaneously charging an amateur magician who has not mastered draining with said artifact's power, by simply placing a hand on their hand/forehead/arm/whatever. Get creative with the application of both charging and draining--it's hard to master individual techniques, but very easy to apply them in fascinating ways with a little experimentation and practice.