I was thinking this morning about the nature of magic items. I've just started reading (for the umpteenth time) The Annals of the Black Company. In the first book the Company is stalking the wizard, Raker, and uses a bit of his hair to bait a trap. Later on, one of the Company's wizards begins making a fell artifact, a black spear, crafting it over the course of his remaining years, until it finally is used to kill a goddess. Here are two different versions of the magic item: Fire and forget, and the Life's Work. I'm much more interested in the latter, and why even a minor wizard like the Company's might be capable of such master craft.
Let's just suppose, to begin with, that being a wizard is something that "bleeds through" into other dimensions and planes of existence. So, the basic laws of thermodynamics get violated, right? Where does that energy come from? Where does it go? It goes into those Places Between, the Ways, the Traveling Spaces, and those places aren't anywhere in particular, but they are very real and very important to magical beings, and beings that use magic. They also are conduits that can be harnessed in various ways through the use of things existing on the material plane (e.g., henges, sacred groves, arcane circles, ley lines, etc.) to get a better purchase on the world, to make it do things it shouldn't. With me so far? Okay, so here's the twist.
What if being a wizard means that, just by being a wizard, you are constantly "bleeding through" into those empty places, where shadows lurk seeking form, and that your magic signature (like a scent) provides the Ones Who Dwell Between with a way to reach you. This may mean they hunt you, certainly, but more like the more powerful you are, the more magic you use, the more likely it is that an unworldly creature of some kind is going to notice you and find a way to use you for its own purposes (e.g., for exotic food, for easy power, for twisted amusements). That being the case, wouldn't you want to, if you're a wizard, figure out a way to keep that from happening? Here's a neat trick: Make the equivalent of a magical heat sink, something to diffuse those energies.
For example (also from the Annals) we have the Silver Spike. Literally a silver nail, but this time forcefully imbued with the power of the Dominator, the most fell wizard of several eras, corrupted in his death with his own deathless essence. It's not an intelligence, necessarily, but an essence of your Self and Craft. Note: that's another thing about being a wizard: Using magic allows you to hang on to life, perhaps without end, just because it works with Law and Chaos in ways that completely remake a wizard's body, over and over again. Sure it corrupts you, but that also means that you're getting additional life in the bargain. Think about that: Magic is a danger, but you have to use it or you will eventually die. You don't want to die, so you have to get as powerful in the use of magic as you can. Doing so puts you in greater and greater peril from the Powers that Be, so you begin to assemble some sort of device(s) or object(s) to serve as dimensional analogs for the shadows that your power casts in the Spaces Between.
In game terms, maybe that means that wizards are always making magic items. They have to, for self-defense. Magic items aren't made with a single spell, or a ritual. Instead, wizards carry objects they've designated to hold this magical essence, and to keep the heat off, so to speak. In time, those mundane objects become empowered, but in peculiar ways, taking on the character of both wizard and wizard's magical history. This is why your magic sword has an ego, and why it has a purpose. It's also why there are magical items just floating around the game world without anyone to look after them. The wizard gets rid of 'em so the magic can't be traced back. As for those poor bastard what have the the items, well... don't be surprised when you get caught holding the bag (of holding).