When I was thinking about treating magic as something inherently demonic in nature and commonly regarded as a violation of the divine order that governs the physical world, I originally had the idea to create a Mage tradition like the Healer or Vowed for priests who are trained in countering and negating the effects of magic. But a tradition means the character has to select 8 different arts by 10th level, and the total pool of arts to pick from should be considerably larger than that. But as it turned out, coming up with 12 different powers that counter magic and can be rationalized as not actually using magic themselves is really quite the challenge. To be a good mechanical representation of the concept, having a pretty small selection of very basic abilities feels a lot more fitting, and so I ended up making the Mage Hunter a single focus instead of a full tradition.
Nothing about this focus is really an original creation by me. All I’ve done is to take already existing mechanics from Worlds Without Number and arrange them in a way to become accessible to a broader range of characters. I think this is a good example to show how easy homebrewing new content to bring your setting to life can be.
Level 1: Gain Magic as a bonus skill, and Effort with a maximum of your Magic skill level plus your Wisdom modifier. You also gain the Sense Magic art.
Sense Magic: Commit Effort as an Instant action; while it remains committed, you can visually perceive magical energy and get a one-sentence description of the effect of any standing magics or magical items you inspect.
Level 2: You gain the Counter Magic and Suppress Magic arts.
Counter Magic: Commit Effort for the day as an Instant action when a visible enemy mage casts a spell. You make an opposed Wis/Magic check against the casters Int/Magic or Cha/Magic skill checks; if you win, their spell fizzles and is wasted. You can use this art no more than once per round.
Suppress Magic: Commit Effort for the day as an On Turn action and target a visible or known magical effect within one hundred feet. The effect is suppressed for 1d6 rounds plus your character level. Spells cast by more casters of a higher level than you may not be successfully suppressed. You can attempt to suppress an effect only once.