The series starts with three kinds of magic: sorceries, miracles, and pyromancies.
Sorcery is a form of magic that is implied to have been created by Seath, the "grandfather of sorcery," the scaleless dragon who betrayed all other dragons for a chance at immortality. Anyone with a high Intelligence and a catalyst (usually a staff of some kind) can cast a sorcery. There are less than 28 sorceries in the first Dark Souls and that number only grew to 39 by the third installment.
Miracles are stories retold so many times that they have become a form of magic, the story evokes an effect. Though miracles do require both a Talisman to cast and a high Faith score. The first Dark Souls has 23 miracles and that number exploded to 38 by the third game.
Pyromancies originated as flame sorceries that only the Witch of Izalith and her Daughters of Chaos knew. When they failed to recreate the First Flame, pyromancy was one of the resulting side effects of their failure. Within the lore of Dark Souls, learning to wield a pyromancy flame requires that you produce the flame from your own body. There is no stat requirement for casting a pyromancy spell. There are only 20 pyromancies in the first Dark Souls, but by the third game there are 30 of them.
(In the second Dark Souls game they introduce hexes, which originate as a subset of sorcery from the Abyss that deals Dark damage, but it is implied that this same Dark magic has tainted some miracles as some hexes are cast the same way that a miracle would be.)
Suppose you apply these forms of magic to D&D. Sorceries are the domain of wizards, miracles would apply to clerics, and pyromancies would most easily fit with druids. Bards would, predictably, dabble with all of them. But a magic system that only requires the proper stat requirement and the tool to use it appeals to me more than a class-based system. The lore behind each spell usually explains where it originates within the game's backstory. Consider the in-game description for Fall Control, the Dark Souls equivalent of feather Fall:
"Sorcery developed by a certain surreptitious sorcerer at Vinheim Dragon School. Reduce damage and noise from fall.
This sorcery, along with Hush, explains the extravagant cost of hiring Vinheim spooks."
What if Mirror Image was just a spell you could find out in the world? And you knew it was developed in a city called Riverport? So if you want it, you'd venture toward Riverport to look for it, right?
These are all things I want for D&D: Lore for spells. An origin of magic. Smaller spell lists.