Great Spirits are beings outside of reality (so are lesser Spirits) that can subject themselves or another to reality.
There are smaller spirits, but I haven’t gotten into that.
The smaller spirits are the souls of humans, my name Spirit of Wrath referencing Berin, the protagonist/antagonist (Madness names him Wrath when he turns) of my story
Worlds means dimensions, and they don’t necessarily work like planets - rather, they are just whatever their Spirit envisions them to be.
There would be two distinct types of magic:
Intended: the Spirit builds in a way to get powers for their reality. This could be seen more as technology - electricity obeys the laws of nature, but it can be used for miraculous things. No examples thus far.
Unintended: There are vulnerabilities within their reality that people can exploit in various ways. An example may be the Servants - any Great Spirit could pull the Thread of a human (where the lesser Spirit is stored in the Archstone, in this case) closer to them, and then the human gains superpowers, able to influence the Threads near them, like fire, cold, wind, emotion.