Alright, this is a weird one--and that's coming from me.
I will preface this by saying--I have no idea how this was possible (though I have a couple theories you can read at the end). The level of specificity in the magick and rituals it must take to make this possible is astounding. I genuinely would never have believed it possible until I experienced it (though the same can said for nearly everything I write here).
This happened about five years ago now. In terms of magick training time, that's an eternity ago. I had just started to really apply any formal training or research to the craft myself, and I was dating a witch at the time who had the most astounding natural energy manipulation skills I had ever seen up to that point despite zero training in it (must have been a speciality in a past life). We were out artifact hunting one day and they excitedly guided me over to a new booth in a then-local antique store. The booth was openly magick themed, full of your usual attractions like sandalwood blocks, chakra balancing crystal kits, and grinding bowls... but also some less savory left-hand-path things like jars full of specific body parts from poisonous animals for black magick rituals and Gu practices (I'm not sure if anybody still practices Gu, but the fact jars of poisonous animal parts were for sale for ritual use definitely puts it in the realm of possibility). This made me immediately suspicious of the nature and motives of whichever magician(s) were running the operation, but such pop-up shops were oddly common here and usually at least had some sort of spell ingredients for sale, so I ended up shaking off these concerns. I shouldn't have done that.
Aside from the seemingly hand-picked black magick ingredient jars, the rest of the booth's fare was pretty sparkling and new and free of energy, presumably sourced from some wholesale supplier. I wasn't a fraction as capable or powerful with aura abilities and reading back then, but I could still get a decent general read on an object's energy (we were artifact hunting, after all). There was a single item that was an exception--a well worn leather bag with a closing strap on top and some vaguely metaphysical patterns engraved/burned all over, seemingly a tree of life and some random sigils. This was a genuine artifact, with a very unique energy property--the outside had a subtle energy signature, not even as strong as a homunculus-in-progress (not that I knew back then what that even was), but the inside of the bag had an overwhelming resonance. It was an energy that, at least at the time, I could not pinpoint as being good or bad, safe or dangerous, or even get a helpful color or astral-core frequency from... but it was ridiculously powerful compared to everything else I'd encountered artifact wise up until that point.
There was a note on the outside of the bag, separate from its for sale tag. To paraphrase: "Use this lovely and powerful bag as a strategic storage spot for all your most important occult treasures." My ex fell in love with the bag at first sight and purchased it to use for this exact purpose. I didn't know any better at the time, and took their theory at face value: that the inside of the bag must have been hexed with an energy-enhancement spell of some sort to revitalize the frequency of any artifacts that were put inside. Cautiously, I allowed them to put one of my less sacred artifacts in the bag and leave it for an hour or so, then took it out to find that the item's energy had indeed gone off the charts and become much more powerful. I was still at a point where charging from artifacts was a crucial part of having enough power to do magick, so I was thrilled and chucked many more of my artifacts at the time in it as well. It seemed too good to be true, like a real life support item from a video or tabletop game: Bag of Keeping, Tree of Life Model, Rareness 999. Ability: dramatically enhances the power and charged energy of any magickal artifacts put inside the bag. This was the coolest shit to ever happen to me!
Until it wasn't.
For a while, the bag worked as intended. Put an artifact with a subtle charge in, let it simmer in the magic bag, take it out and it's hypercharged. You could basically get endless etheric energy charges this way. It seemed like cold fusion for magick! Until one day, I put my most powerful artifact inside. Not for the first time, but for the first time for more than a few minutes to test. My ex put their most powerful artifact inside too. We left it overnight, and...
...the charge in the artifacts was nearly entirely gone.
Baffled, I threw the items out of the bag and scanned it for energy signatures again. The previously elusive energy had changed to one that was functioning as a vaccuum. Once we had gotten in the habit of using the bag and trusted it, its true nature was revealed and it had turned into a remote funnel to absorb power from our artifacts and send them to another magician, presumably the one who sold us the bag. I had my ex check the energy in the bag and in the artifacts and they, devastated, reported the exact same readings. I was heartbroken--my strongest artifact from that time has never been able to regain that level of energy charge since, and thus became nearly worthless as an artifact for my purposes at the time. I'm at the point now where it wouldn't have sufficient power to charge me to max even when it had been in its hypercharged state, but for several years this was actually a massive setback. I have no idea where the bag is now. When my ex left I told them I didn't want the bag in my house and that if they wanted to keep it for some reason it was all theirs. I don't know if they kept it as a curiosity or chucked it out.
I've spent many sleepless nights since then laying wide awake trying to reason my way through how this type of magick attack was even possible. The bag itself never left our possession or my room, so the hexer couldn't have done anything to it physically to trigger its shift. While I had initially pictured this being the work of a complex multi stage hex (place an energy boosting spell inside with a timer that eventually shifts it to an energy draining and transferring spell!?), I've yet to find any documentation of such a thing being pulled off successfully, and it honestly sounds a bit too complicated to be feasible with any methods I've used (or had used on me) in the past. Recently I've been revisiting the story in my mind and thinking through it with the new information and abilities I've become familiar with since, and I have come to the conclusion that it must have been either a spirit being utilized intentionally, or the result of an accidental homunculus.
Considering the ability a trained magician has to remotely communicate with and command their own trained and programmed spirits, a spirit being bound to the inside of the bag would be the most likely culprit. The magician likely created a spirit for this purpose, bound it to the inside of the bag, monitored the energy it was interacting with to see when and with what we were using the bag, then had the spirit change its mission to draining and transferring that energy back to the user once our most powerful artifacts had been placed within reach. This kind of wildly complex spirit work is not something many will ever become capable of, and it's beyond my current abilities with local spirits, but I've managed enough of the individual components of spirit work that go together to make it possible that I can understand how this would technically be possible. And, back then, I had zero training with spirits... not in detecting them, making them, fighting them, communicating with them... so while I could confidently today say if an item has a spirit bound to it or not, that was sadly above my level when the bag was in my possession.
The alternative I've thought of as well is that the energy in the bag was simply incredibly powerful due to whatever happened to it or near it to make it into an artifact to begin with, and that this overwhelming energy would often spread to items we'd place in the bag. At some point, by adding so much more energy and so many types of energy, the formless mass of powerful magical/etheric energy undertook whatever triggering process it takes to spark the creation of a homunculus, and the new energy signature in the bag was now of this homunculus itself. Homunculi consume energy to grow and evolve, so the draining of our artifacts may well have been the result of the homunculus becoming active and feasting on our artifacts instead of the fault of an intentional attack from the seller. If this theory is the correct one, this would possibly be my first encounter with a homunculus chronologically. Like with spirits, I had not even considered the concept of a homunculus at that point in time and hadn't yet developed techniques to detect and distinguish them. I wish I had a way to confirm or deny this theory, as it may bring further hints to the still-mystery of what exactly happens to an artifact that causes its energy to spontaneously become an artificial lifeform of sorts... but it is what it is.
Regardless, this all happened in the span of a few weeks and when I went back to see what else the seller had for sale and attempt to further feel out their possible motives and intentions, the booth had vanished without a trace. Unlike other similar ones I've seen, it never had a proper name or any way to contact the seller given, either, so I had nothing to go off of when it was just suddenly... gone. That may be another part of why the whole thing still feels so perplexing to me to this day.