Clinging Breath( Draconomicon, p. 67)
Your breath weapon clings to creatures and continues to affect them in the round after you breathe.
CON 13, breath weapon,
Lingering Breath (Dr) ,
Your breath weapon has its normal effect, but also clings to anything caught in its area. A clinging breath weapon lasts for 1 round. In the round after you breathe, the clinging breath weapon deals half of the damage it dealt in the previous round. Creatures that avoid damage from the breath weapon (such as creatures with the evasion special quality or incorporeal creatures) do not take the extra damage. For example, an old silver dragon uses its cold breath and deals 72 points of cold damage (or 36 points against a target that makes its save). In the following round, foes that failed their saves against the breath weapon initially take an additional 36 points of cold damage, and foes that succeeded on their saves take 18 points of cold damage. A foe can take a full-round action to attempt to remove the clinging breath weapon before taking any additional damage. It takes a successful Reflex saving throw (same DC as your normal breath weapon) to remove the effect. Rolling around on the ground grants a +2 bonus on the saving throw, but leaves the foe prone. A clinging breath weapon cannot be removed or smothered by jumping into water. A clinging breath weapon can be magically dispelled (DC equal to your breath weapon save DC).
This feat only works on a breath weapon that has instantaneous duration and that deals some kind of damage, such as energy damage (acid, cold, electricity, fire, or sonic), ability damage, or negative levels.
When you use this feat, add +1 to the number of rounds you must wait before using your breath weapon again.
You can apply this feat more than once to the same breath weapon. Each time you do, the clinging breath weapon lasts an additional round.