In fantasy stories, magic is often the product of interactions with intelligent supernatural beings - gods, spirits, or what have you. This at least gets away from the pseudo-technological feel of most gaming magic, but it raises an obvious question: what's in it for the gods?
Well, the gods can be interested in a lot of things. Maybe they just need to be worshipped, as in Pratchett's Small Gods. Maybe they have a scientific curiosity in mortals, and magic is just a reward system in their experiments. But I've always thought those ideas were too human-centric, depending on humans being inherently fascinating or valuable to gods. Here's another idea, free to use for either gaming or fiction:
The gods live in their own universe, completely separate and unreachable from the human universe. Their lives are mostly incomprehensible, but one of the things they have in common with us is conflict over resources. Thousands of years ago there was a big conflict over a valuable resource - whether this was more like the Gulf War or two cavemen punching each other over a deer carcass, we can't say. Anyway, somehow in the middle of the conflict the resource was shattered and fell into our universe, with a shard of it ending up in every living thing. The shards vary in size from tiny in simple plants to enormous in humans, but they're absolutely undetectable to human senses and cause no effects. Except that they provide a link between the gods' universe and ours. Gods can use the shards to produce magical effects in any living thing that has one. They can cure illnesses and heal wounds, make trees walk, let people fly, and basically do any magic that involves living things. Whenever something with a shard dies, the shard gets transferred to an appropriate new lifeform for its size. This does not mean that reincarnation exists - the shard has nothing to do with a soul.
So, the gods can perform all this magic, but what's in it for them? Well, they really want those shards back, they're even more valuable in the gods' universe now than when the conflict happened. But getting them back is damn tricky, since performing magic with a shard entangles it more in our universe and makes it harder to pull back into theirs. It doesn't help that gods can only perceive our universe as an arrangement of shards. What they need is a human who can take an animal or plant with a shard and kill it at just the right moment, when the god is ready to yank the shard back into its universe. The human gets a certain amount of magical assistance, the god gets whatever the shards are made of. Everyone's happy. Except the victims of the inevitable human sacrifices, which deliver far larger and more valuable shards than animals. Actually the necromancers run into a problem - the human population's increased so much since the conflict that most people don't have a shard and are entirely immune to magic...