This power causes you to grow long horns while in Draconian Form, changing your headbutt to inflict stab damage, and giving it +2 Attack, Damage and bypass per rank. All three bonuses are increased to +3 per rank if you have Pierce, or +4 per rank if you have Great Pierce.
In addition, your movement rate is increased by +1 per rank, or +2 per rank if you also have Sure Footed. This doesn't apply while flying.
At rank 10, your headbutt performs an internal stab burst when it achieves a critical hit, as long as no other headbutt burst attack has been performed (for example if your headbutt has a 50% chance of performing a cold burst, then the stab burst will only be performed if the cold burst fails to activate).
At rank 20, your headbutt only has to inflict damage to perform the burst.