Grigori

Dragons are creatures wreathed in mystery. Though they have appeared a handful of times in the long history of the continent, it is still not clear how they are born or what brings them to attack men’s civilizations. The small amount of knowledge that has been gleaned from their sporadic attacks reveals little more than the facts that dragons possess dreadful power and are intelligent enough to understand human speech.

Dragons appear without warning, sometimes dozens, sometimes hundreds of years apart, bringing chaos in their wake and destroying men and nations without distinction.

Their actions are inhuman and atrocious, but given their high level of intelligence, it is hard to imagine that their violence is without purpose. Many times in the past have they brought the world to the edge of destruction, but they have never completely wiped out mankind.

In every age that they appear, the dragons commit a short-lived but ferocious assault upon the world. Then they cease their attack and alight atop a mountain or other visible location, as if waiting for something. Given these strange actions, it is possible to think that the dragons are fulfilling some sort of role or duty, serving some greater function in the world, yet at present there is simply not enough evidence to make any sort of theory about the dragons’ purpose.

It is also clear from past records that the number of monsters in the world seems to sharply increase around the time that a dragon appears. This could be nothing more than coincidence, but if it is somehow an effect of a dragon’s imminent appearance, then this would be another example of dragons’ peculiar place in the natural order of the world.

Item Drops
*Post Game

Tactics

 * The first part of your final battle with the Dragon will involve both escaping and chasing it. The final showdown commences when you both land in a wide open area.
 * The Dragon's heart is its main weakness. It must be exposed and exploited to inflict significant damage.
 * If The Dragon decides to fly away and attack from out of range, Ballistas located around the battlefield can be used to ground it again.
 * The Dragon cannot be defeated unless the final blow is landed on its heart.

Rewards
All items equipped by the Arisen are Dragonforged, and the Godsbane will appear in your inventory. In addition, you will recieve one or two weapons equivalent in type to those equipped by the Arisen, as well as a Crimson Dragon Scale.

(SPOILER WARNING)

Story
The Dragon appears, creates an Arisen, then takes refuge in the Tainted Mountain, waiting for the current Arisen to challenge him. You encounter him finally in the aptly named quest, "The Final Battle". Upon completing "Deny Salvation", the previous story quest, your beloved will dissapear from the world, as he or she has been captured by the Dragon.

Upon reaching The Dragon, the Arisen is given a choice. The first is to sacrifice your beloved - upon doing so the Dragon will agree to leave Gransys for a time, eventually returning some years later., granting you immortality and Dukedom of Gransys as long as the Dragon remains alive. It is then revealed that Duke Edmund Dragonsbane took this bargain, and had lied about slaying the Dragon - those that gave their hearts to the Dragon remain immortal until the Dragon is slain.

Your second choice is to fight the Dragon. Your beloved is given the chance to escape as the room is destroyed, and you and your pawns escape it's wrath to a more favourable location to fight it. Eventually the Arisen scales the dragon, reaches the point where the Dragon keeps your heart, stabs it, causing you and the Dragon to tumble to the ground, where the battle is continued until the end. Once Grigori is slain, all remaining Arisen have their hearts returned to them and they become mortal once again - the Dragonforged turns to dust immediately, having escaped death for many years, whilst Duke Edmund becomes a frail old man.

Unfortunately, the Dragon's death does not mean the salvation of Gransys. The Everfall located beneath Gran Soren opens in its entirety, destroying most of the city and unleashing more ferocious monsters upon the world, as well as The Long Night, an eternally darkened sky. It's clear at this point that the death of the Dragon does not mean the end of the Arisen's journey.

Trivia
(Some of the lore of Dragon's Dogma discussed here is based on fan speculation and theory, it should not be assumed as canon)
 * The Elysion refers to the dragon as "Grigori", a name which the Dragon also speaks during the incantations used to steal your heart. It is therefore assumed that Grigori is the dragon's real name.
 * The Dragon's language is Latin. Grigori speaks it during the first encounter with the Arisen, then later begins to speak in English. It could be interpreted as an ancient language in the Dragon's Dogma universe, known instinctively by Dragons - the unique Drake and Wyvern (as well as generic dragonkin) speak in Latin, whilst the Wyrm in Watergod's Altar speaks to the Arisen mostly in english, referring to you as a "fellow countryman".
 * Grigori is the name given to the angels referred to as "the watchers" in Biblical mythology. The Dragon's winged appearance, its resistance to Holy magick, and the image displayed in the loading screen (revealed in full during the credits) give it a strong angelic motif in the mythology of Dragon's Dogma.
 * The Dragon also bears a thematic resemblance to the Grigori. It is the being that watches over the world, finding new Arisen as candidates to take on the role as the Seneschal. Similarly, an Arisen that loses to the Seneschal will fall from grace to take on the form of a Dragon.
 * The Dragon that speaks to Savan in the prologue and the Dragon that takes your heart bear the exact same voice, despite the two Dragons existing a long time apart. This leads to the theory that whilst Arisen do become Dragons, it is only their bodies that do - they become empty vessels for the being known as Grigori to reincarnate into, which then seeks out and tests new Arisen. Grigori seems to have an in-depth grasp of human history from perhaps before Savan's era, and it is possible he has experienced death many times. This idea is supported somewhat by the opening sequence; a dragon arrives at Cassardis intent only on mindless destruction, but upon being challenged by a human, Grigori awakens (indicated by a change in eye colour from grey to a glowing red) and recognises a candidate for Arisen. This might explain why the Dragon has such a dangerous history - should the Arisen lose to Grigori, he dissapears, leaving behind a soulless beast to attack mankind.
 * European Dragons have always been depicted as the ultimate evil, but have always been used to transcribe challenges, or hardships. One example of this is the classic tale of a knight saving a princess from a dragon - this theme is referenced somewhat in your rescuing of your beloved from the Dragon.
 * Killing the Dragon with a sword equipped will earn you the titular Dragon's Dogma as one of your weapon rewards. With no specific uses of the word "Dogma" within the game, though its definition has an obvious relation to story, it's possible this weapon was imagined first and the choice of the game's title followed.