Malformed Vocal Cords (3.5e Flaw)
From D&D Wiki
Malformed Vocal Cords
In gaining the breath weapon, somehow your vocal cords were altered so that you speak exclusively in draconic.
Effect: You suffer an innate 10% chance of spell failure with any spell with a verbal component. You cannot speak any language other than draconic, even if you know and understand other languages.