Breath attack is a special ability typical for living dragons, but also for Firebirds and Phoenixes. It enables them to attack two consecutive hexes at once, making individual damage to both hexes. However, creatures that are two hexes wide do not suffer double damage from the breath attack. Although creatures with breath attack specialty cannot directly attack allied creatures, they can - similar to Liches' Death Cloud and Magogs' Fireball Attack - cause damage to allied creatures located on the second hex. In other words, breath attack will also damage hero's own troops if they are standing directly behind the attacked hex.
Certain other creatures like Mighty Gorgons have an attack that visually looks like breath attack, but does not have the same effect.
Creatures with breath attack: