I always think the setting itself is a character in these stories, and the best ones actively work against the combatants. A sprawling, decaying port city during a storm, for instance—empty warehouses, slick docks, a rising tide. It’s not just a backdrop; it forces movement, creates hazards, and obscures allies from enemies. You can't easily escape the downpour, so you're always seeking shelter that might be someone else's lair.
There's also a lot to be said for a gothic, labyrinthine royal capital. Think narrow cobbled streets that twist into dead-ends, towering cathedrals with spires perfect for snipers, and ancient catacombs beneath. The history weighs on everything, making every Master wonder if a ritual circle from a previous war is hidden under their feet. The sheer density of architecture turns every confrontation into a claustrophobic mess, with no clean lines of sight.
But honestly, I find the most tension comes from taking the 'holy' part literally. A remote, sacred island monastery cut off from the world—nowhere to run, ancient wards interfering with magic, and a single, central relic everyone must converge on. The isolation is the killer; no outside help, no easy resupply, just you, six other mages, and a lot of stone corridors echoing with whispers.