Dragonthrall( Draconomicon, p. 105)
You have pledged your life to the service of evil dragonkind.
Speak Language (Draconic),
You gain a +4 bonus on any Bluff check made against a dragon, and a +2 bonus on Ride checks made when you are mounted on a dragon. You gain a +4 bonus on saves against the frightful presence of evil dragons. You take a —2 penalty on saves against enchantment spells and effects cast by dragons.
You can't select this feat if you have already taken the Dragonfriend feat.