I've taken my time in actually reading them, but Steven Erikson's Malazan Book of the Fallen series and Ian C. Esslemont's Tales of the Malazan Empire are a great series of books.
I'm not finished with Erikson's 10 novel saga, or with Esslemont's 5 novels (the fifth due out in November), but I really enjoy their setting, and especially the fact that it morphed out of their own D&D and GURPS games.
The novels present a gritty world, with plots and betrayals, and ascended demi-gods, and a unique flavour to the magic and how it works, and undead Neanderthal warriors, and shape-shifting packs of wolves and all kinds of other fun that I don't need to get into. Instead, you should go read them all!
Anyway, long story short, I want to go and visit, so I've been thinking about how to adapt my rules system to fit, and I think it works well enough, providing the setting itself is adequately explained.
Having access to a Warren is what lets a person use magic, and whilst some characters have access to several, rarely do they have mastery of more than one (Quick Ben is an exception, but he has a loophole).
So it seems that a Mage's abilities might list traits like Warren of Rashan, or skills like Travel by Warren. In more powerful cases, they might have Magi of High House Shadow, although that puts their power level a bit higher.
A character could work towards ascendancy, or wander the landscape with an item invested by some warren or god (perhaps having somehow gotten hold of a T'lan Imass weapon). It all seems to work reasonably well. I think it needs some heavy stress testing though.
I'll keep everyone informed of my progress!