Books

Malazan Book of the Fallen is fairly soft due to complexity and overlapping systems. A dozen or so themed sources of magic(warrens), several older sources of power (holds) and several powers specific to certain species.

Some characters can access several of these sources and one character semi-accidentally creates a supplemental system that might be more rules based. Geographical location matters and the warrens/holds are also physical realities separate from the main one with their own hazards.

Also, there are mysterious elder entities and there's always the possibility of ascending to godlike powers through a parallel system of high houses roughly aligned to warrens and mysterious buildings but defined by an in-universe tarot deck that can be altered...