Yaaay this sounds like fun!

Here's one for NeoPhoenix!

Phoenix Fever

Acquired from handling fire-based magical creatures without special protection

Fort DC 18; incubation 1 day; 1 CON damage/day (can't be restored without removing the disease), each time you take damage from any source, you also take 2d6 fire damage; if you are slain, your body bursts into flames, dealing 1d6/HD damage to all targets within 10 feet (DC 14 Ref half), if anyone took damage, they must succeed on the Fort save or contract Phoenix Fever.