Lingering Breath( Monster Manual IV, p. 203)
Your breath weapon forms a lingering cloud.
Clinging Breath (MM4) , CON 15, breath weapon with a recharge measured in rounds,
Your breath weapon has its normal effects, but also remains as a lingering cloud of the same shape and size as the original breath weapon. This cloud lasts 1 round. Foes caught in the breath weapon's area when you breathe take no additional damage from the lingering breath weapon, provided they leave the cloud by the shortest available route on their next turn. Otherwise, anyone who touches or enters the cloud while it lasts takes one-half of the breath weapon's normal effects; any saving throw the breath weapon normally allows still applies. Damaging breath weapons deal one-half their normal damage, and breath weapons with effects that have durations last for half the normal time. If a creature is affected by the same nondamaging breath weapon twice, the effects do not stack. For example, an old silver dragon uses this feat on its cold breath weapon. Creatures caught in the 50-foot cone take 16d8 points of cold damage, and a DC 31 Reflex save reduces the damage by half. The 50-foot cone lingers for 1 round. While the cone lasts, anyone touching or entering it takes 8d8 points of cold damage, and a DC 31 Reflex save reduces the cold damage to 4d8 points. Creatures in the cone when the dragon breathed take no additional damage if they leave by the shortest available route on their next turn. If the same dragon uses this feat on its paralyzing breath weapon, a creature caught in the 50-foot cone must make a DC 31 Fortitude save or be paralyzed for 1d6+8 rounds. The 50-foot cone lingers for 1 round. While the cone lasts, anyone touching or entering it must make a DC 31 Fortitude save or be paralyzed for 1d3+4 rounds. Creatures in the cone when the dragon breathed take no additional damage if they leave by the shortest available route on their next turn. Creatures paralyzed by the initial breath cannot leave the cloud, but suffer no additional effects because the paralyzing effects do not stack. When you use this feat, add +2 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 lingering breath lasts an additional round. You can apply this feat to a breath weapon that also has received the Clinging Breath feat, but the resulting breath clings only to foes caught in the initial breath.