"Within the Warren of Chaos, Quick Ben knew of the innumerable shifting pathways that led to doors. Though he called them doors they were in fact barriers created where Warrens touched, a calcretion of energy as solid as basalt. Chaos touched on all realms, with gnarled fingertips bleeding power, the doors hardened wounds in the flesh of other worlds, other avenues of magic.

(...)

Each Warren of magic possessed a smell, each realm a texture, and though the pathways he took were never the same as he'd taken before..."

GotM, US HC, p.271

Aspects: Warrens and Holds

"'(...) What's a warren?'

'(...) It's a path of magic. The forces that govern all existence are aspected...'

'Aspected. In the way the Holds are aspected?'

'The Holds.' He shook his head. 'Sitting in a wagon with square wheels and complimenting each other on the smooth ride. That's the Holds, Acquitor. They were created in a world long gone, a world where the forces were rougher, wilder, messier. The warrens, well, those are wheels without corners. (...) Paths of aspected magic. Like forces and unlike forces. Right? Unlike forces repel, and like forces hold together, you see. Same as water in a river, all flowing the same way. Sure, there's eddies, draws and such, but it all heads down eventually.'"

MT, US Kindle, Chapter 21