ToME WikiOrvin: Two ideas concerning flaming arrows:
1) For fire-branded arrows, add a chance, when they land/hit a target, of their causing a fire spell effect within a certain radius. The chance and radius would increase with Archery skill (maybe a max radius of 3 and max chance of 20%). The chance for a square within the radius would also depend on its terrain (according to flammability).
2) Add another means of creating flaming, but not fire branded, arrows. These would be an option when making arrows, require not only suitable arrow-material, but also a filthy rag and oil (the rag would be consumed in the process, the oil not). When launched, the player would automatically light these arrows with his light source and they would do damage as if fire branded, and have a chance of catching nearby things on fire, as above. However, these arrows would disappear, unlike fire branded arrows.