Any character can take Pyromancy as a Class Talent
All of your attacks deal fire damage whether you want them to or not. You treat creatures that are naturally immune to fire damage as only Resist 16 Fire, and ignore resistance on creatures who have resistance to fire damage.
Adventurer Feat: Treat creatures with no resistance or immunity to fire damage as Vulnerable Fire.
Champion Feat: Fire and explosions go hand in hand. Once per day when you hit with a natural 16+ and deal damage, repeat the attack against 1d3 enemies nearby the original target and deal half damage.
Epic Feat: You are immune to Fire damage. Sunburns are a thing of the past. You don't ignore cold damage, but cold weather doesn't bother you much any more. Fire good. Fire very good.