Fire Cloud

Area 
Creates a swirling cloud of flames and fiery embers. It does not block vision, but inflicts burning damage to all within it. Creatures in the cloud take damage on their own turns. If less than an entire second is spent in the affected area, damage is halved (round down). Armor protects normally. Only highly flammable materials may catch fire.

Duration: 10 seconds. 
Base cost: 1 to 5; the cloud inflicts 1 point of damage per second for every energy point put into the base cost. Same cost to maintain. 
Time to cast: 1 to 5 seconds, depending on base cost. 
Prerequisites: Shape Air and Fireball.

Item 
Staff, wand, or jewelry. Usable only by mages.  
Cost to create: 175 energy and a $500 ruby.