Dragon Force

Dragon Force (ドラゴンフォース Doragon Fōsu) is an advanced Dragon Slayer ability.

Description
When a Dragon Slayer enters Dragon Force, they effectively turn into a humanoid Dragon, gaining reptilian scales and traits, such as further elongated, and sharper, canines for First Generation Dragon Slayers, and scaly arms, sometimes complete with claws, for Second Generation Dragon Slayers. According to Zero, Dragon Force is the final, most powerful state a Dragon Slayer can attain; granting them power comparable to that which a real Dragon possesses: the power to utterly destroy everything.

Abilities
Dragon Force greatly increases the damage done by standard Dragon Slayer spells, and grants the user access to more advanced, powerful attacks. It also drastically enhances the user's physical prowess, making them far stronger, more resistant and faster, and considerably boosts their Magic Power, which becomes visible, taking the appearance of a Dragon. When exuded at its fullest, said Magic Power takes on a violent corporeality, likely as a result of the immense amount of Magic power employed. When Natsu Dragneel entered this state through the use of Jellal Fernandes' Flame of Rebuke, his flames gained the ability to burn off offending Magic, even that of Zero's ultimate attack Genesis Zero.

Achieving

 * For First Generation Dragon Slayers, those who have been taught their Magic by a real Dragon, certain conditions must be met in order to enter Dragon Force: the only one known so far would be to eat substances with powerful Magical properties, preferably those somehow related to the element they can control and consume; while other, unrelated substances can be eaten as well, these have been described as being similar to "poison" for the user, causing heavy after effects, such as pain on activation and extreme exhaustion after use. However, it is likely that, due to it being considered the final state a Dragon Slayer can attain, a First Generation Dragon Slayer may eventually be able to freely enter Dragon Force without outside sources of power, like the Third Generation. So far, Natsu Dragneel is the only First Generation Dragon Slayer to have entered Dragon Force, doing so on two occasions: first through the consumption of Etherion, and then from Jellal Fernandes' Flame of Rebuke.