Gurps Monster Hunters: Pyromania
You like fires, explosives and their related effects. You look for all legal or safe opportunities to set or watch fires/explosions and their effects whenever possible, and will fight to be the one in charge of the campfire. While engaged in setting or watching fiery displays, your DX, IQ and all sub attributes, and skills are at a penalty for anything unrelated to the fiery matter at hand (based on your Self Control level). If an emergency crops up while you are fire-watching, make a Self Control roll or Do Nothing as you ignore it in favour of fire-watching (roll against IQ each second, with a cumulative +1 per turn after the first, to snap out of it). You snap out automatically if the fire is extinguished.
This distraction and fascination extends to combat situations. The sudden appearance of new fires of torch-size or better (or fiery jets and explosions) force a self-control check on your next turn or you must Do Nothing. Declare your action for the turn first, then make the self-control check - the GM should give a bonus if your action either takes you toward a vantage point where you can see the better, or is aimed to create more fire to appreciate. "I run directly towards the fire, right through the caltrops!" is good for a +4 at least, casting a 1 second Fire spell is good for +2 or +3, and starting a longer action to make fire is always good for at least a +1.
If you fail, you are not stunned, merely passive - you can still defend yourself and at no penalty, but you may not take Retreat options other than Dodge and Drop if they will take you further away from the pretty fire. Roll IQ with a cumulative +1 modifier for each second you have spent Doing Nothing to snap out of it. You snap out automatically if the fire is extinguished.
Even if you succeed, your DX, IQ, and skills will be penalized based on your Self Control level until the fire is removed or you get a chance to really appreciate it (voluntarily start Doing Nothing as per a failed check). This penalty does not apply to actions that either take you closer to the fire so you can watch it, or would create more fire! Note that explosions and Fireball spells generally remove themselves nigh instantly resulting in a single turn of Doing Nothing, but any secondary fires started may cause distraction.
People who are being inconvenienced by your fire-watching will react to you at -1, due to the difficulty of getting your attention. This reaction penalty rises to -2 when you are being considered for stewardship over a large supply of flammable or explosive materials, or over a large fire. You're not actually an Arsonist, but you make people worry sometimes.
Fire mages with mild Pyromania can sometimes seem a little Berserk - usually able to cast one fire spell after another but otherwise ignoring any plan or tactics or situation that doesn't involve spreading more fire. Fire mages with severe Pyromania are fairly dysfunctional, as they cast one spell, and then stop everything to marvel at it.
Pyromania Self Control Table
As Pyromania, above, but you look for any, legal or otherwise, safe or not, opportunity to set and watch fires... Make a Self Control check in any situation where you have the means to light a fire and something combustible to burn, failure indicates you must immediately start working on setting the fire. You are allowed to take reasonably simple actions to preserve your own safety (taking the garbage can full of shredded paper outside, laying down a fuse or gasoline trail so you can be outside the building when igniting it) but you should be able to explain to the GM how your actions directly contribute to the immediate goal of burning that thing.
People who witness your obsessive relationship with fire will react to you at -2. This reaction penalty rises to -4 (or higher!) when they realize you're anywhere near a large supply of flammable or explosive materials.
Do not let this character have matches or the Ignite Fire spell. Generally not a suitable disadvantage for PCs.
Quirk: Really Likes Fire
You generally act like someone with the Pyromania disadvantage, without the risk of having to Do Nothing in an emergency. You may periodically suffer -1 to actions due to being distracted by a particularly "good" fire, at the GM's discretion.