A War Hydra with this upgrade has a Breath Weapon with the Flaming Attacks special rule. The Strength of this attack is equal to the War Hydra's remaining Wounds.
Source: Warhammer Armies Project: Unofficial 9th Edition
A War Hydra with this upgrade has a Breath Weapon with the Flaming Attacks special rule. The Strength of this attack is equal to the War Hydra's remaining Wounds.