Miserable Little Piles of Magic (Magic systems, cottonmouthed)
For Glaugust '26, prompt 5-4: Cottonmouth a pet system. As I am extremely indecisive, I'm instead going over multiple methods of doing cottonmouth for various magic systems. Hopefully one of these resonates, because the question of "What is an MD" has haunted my mind for too long. Usual thanks to the GLOG server for helping me with some of these ideas (or just having them separately so i can steal them), particularly Pillar of Worms and CyberJazzFusion.
Classic Vancian Magic
This is easy. It's already been done by multiple people. Spells are weird little spirits you've bound/convinced to help you, and they cast themselves once per day. Multiple casts are either having multiple of one spirit or having a stronger or more cooperative one. If you really want to lean into this, you can make each spell a little familiar you actively communicate with. With that said, let's move on to the trickier options, like...
MD
Wouldn't be a GLOG post without addressing these little things. MD are larger, more discreet units than an MP pool, and so they could easily take the place of spells as Little Spirit Things. The specifics could be imps, bound souls, foxes, fairies, or whatever else you come up with. A low, non-expending roll is the spirit producing a small effect without exhausting itself, while a high roll is the thing giving its all. By spending multiple MD, you're having multiple little familiars work on the same spell, and the mishaps that come from doubles are what happens when they fight or rebel against you. This variety works particularly well if you want "typed" MD that can only work on specific spell schools, have different die sizes, or even count as multiple dice.
Alternatively, the MD could be something more non-sentient. For example, they could represent stolen or inherent divine fire, imbued directly into yourself. Each MD could be a "spark" that powers your various spells (probably fire magic), and the more you use, the stronger the effect as you pump in more energy. For a third option, MD could be physical objects, such as the classic head-orbiting Ioun stones. This, of course, makes MD physically possible to steal from the wizard using them, though you'd need to be very close and have quick hands.
Magic Points
Your classic mana meter from Videos Games. As TTRPGs don't work well with huge numbers, you need an easier to handle amount of points, small enough that you could represent them with spirits yet again. Due to the quantity, this works best with things that can operate in swarms, like Zelda-style fairies or really tiny demons.
Alternatively, you could take the phrase "mana pool" to its logical conclusion and make magic an actual liquid. Perhaps it sits in a pool at your home base, in which case it can be found and defiled, or perhaps modified to enhance it. Maybe you keep it in ampoules on your person, to be used up when needed, though this also risks theft. It could even be a fluid in your blood and your magic pool is your BMC (Blood Mana Concentration). You can technically go over the max using potions or directly injecting the stuff, but this is liable to have Consequences.