Primal Dialga

Primal Dialga (Japanese: やみのディアルガ Dark Dialga) is a Pokémon that appears in and. It is located at the pinnacle of Temporal Tower, and is the final boss of the game's main storyline.

Primal Dialga is actually after losing control of its ability to manipulate time due to the collapse of the Temporal Tower. In this form, it is also incapable of logical reasoning or showing mercy, only seeking self-preservation and preventing time from flowing properly. The player must return the Time Gears to the tower to restore the flow of time, calm down Dialga, and prevent the future where darkness rules.

Like all Dialga, this one is treated as genderless for gameplay purposes; however, it is addressed with masculine pronouns in dialogue.

Physiology
Primal Dialga has the body shape of a normal, but the color scheme is different. The blue color in its body is changed to dark navy blue, the "streamers" are recolored to orange, and the diamond in the chest is altered from blue to a cherry shade red, which is a sign of its berserk and savage state. This is caused by a collapsing Temporal Tower, resulting in complete loss of self-control, which earns it the name of "Primal Dialga".

Background
The Primal Dialga state is a result of 's act of stealing the Time Gears; with the flow of time disrupted, Dialga becomes corrupted along with time itself. In an alternate future, Temporal Tower collapses, sending Dialga into an uncontrollable rage and reducing it to a being running on primal instinct. In this state, it seeks only self-preservation, and does whatever is necessary to thwart any attempt to alter the past (and subsequently erase it from existence). When and the player go back in time, Dialga sends its henchman  back in time as well to stop them. Primal Dialga is first seen after Dusknoir drags the player and their partner back to the future, where Primal Dialga orders Dusknoir to eliminate them. He then assists his six in trying to stop the group from going back in time once more, but fails due to the partner's quick thinking; Primal Dialga stops Celebi's time travel before they can reach the Passage of Time, but this still isn't enough to prevent their escape.

Once the player and partner reach the summit of Temporal Tower, the present day Dialga attacks them, believing they've come to destroy the Tower due to being in the process of transforming into Primal Dialga. They manage to defeat him and save the tower, restoring time and Dialga to their normal states, after which he thanks the player and their partner, grateful for all they've done. The future Primal Dialga, Grovyle, Dusknoir, and the player are all erased from existence, as they come from a future which no longer exists. After the Temporal Tower incident, the present day Dialga returns the player to life as a show of gratitude for repairing the flow of time and the player's sacrifice, as well as the partner's sorrow at the loss of their friend.

However, as revealed in the Special Episode In the Future of Darkness, before they are erased from existence, Primal Dialga proceeds to punish Dusknoir for his failure, as well as Grovyle for trying to change the past. However, they escape, and eventually it's revealed that Primal Dialga's order was a plot for Dusknoir to take over Grovyle's body and return to the past to alter it. What Primal Dialga didn't count on was Dusknoir sympathizing with Grovyle and saving him at the last second; in response to this, Primal Dialga viciously attacks Dusknoir for his betrayal. In that moment, time starts to flow as a result of the player's victory in the past, and the returning flow of time affects Primal Dialga, causing it to go completely berserk and act on pure instinct, which leads it to the Passage of Time at the peak of Vast Ice Mountain. Primal Dialga then battles Grovyle, Dusknoir, and Celebi, but is beaten. After the dark future is erased, Dialga, Dusknoir, Grovyle, and Celebi are spared, and Dialga is restored to its normal state of being. He then informs them they were likely saved by.

The Dialga battled at Temporal Tower is not actually the same as the one from the future Grovyle comes from; when battled, Dialga still has a shred of its self left, and thus is not completely "primal" yet. This is shown by the future Primal Dialga only being able to communicate with growls and roars (which Dusknoir apparently understands), while not-quite-Primal Dialga is able to speak to the player and their partner using broken words.

In the anime
Dialga made two very brief appearances in Pokémon Mystery Dungeon: Explorers of Sky - Beyond Time & Darkness. It first appeared in its normal appearance in the opening sequence, and then it appeared at the end of the special as Primal Dialga, though it was a mere silhouette.

In the Pokémon Mystery Dungeon: Blazing Exploration Team manga
Primal Dialga appears as a major antagonist in this manga, serving the same role he has in the games. He first makes his appearance in the Dark Future, where Dusknoir takes him to attack Honō,, and Grovyle. Despite Dialga's intimidating presence, Honō is unfazed by it and attempts to attack, only to be retaliated with a blast of energy. Having no choice, the group attempts to use Celebi's powers to escape back in time, only for Dialga to make their efforts pointless with its own control over time.

After managing to get back in time when Celebi sacrifices herself, Honō and Totodile make their way to the Temporal Tower so that they can prevent the present-day Dialga from turning into its destructive Primal form. Upon arriving, they encounter a much less violent Dialga, who believes that the two are attempting to the destroy the tower and plans on stopping them. During the battle, the tower continuously collapses, causing Dialga pain and turning him into the feral Primal Dialga little by little.

After a long battle, Dialga is finally defeated when Totodile puts the five Time Gears into their slots, fixing the Temporal Tower and turning Dialga back to normal. Now back to normal, he thanks the two for their courage to stand up to him. When the result of changing history causes Honō to disappear from existence, Dialga uses his power to bring him back to life once he senses how sad Totodile was.

Trivia

 * Although Primal Dialga has lost control of its power, it can still warp through time and use its signature move.
 * Six years after Primal Dialga's introduction, Primal Reversion was announced, with the Pokémon who have used Primal Reversion being identified by the word "Primal" in front of their names, like Primal Dialga. However, this is unrelated, as Primal Dialga is referred to as "Dark Dialga" in Japan, whereas the Pokémon who undergo Primal Reversion are referred to as "Primal" in Japan.