This page is shamelessly ripped from Winds of Change, my FFXII fansite. It also covers Ashe's role in the entire plot, so beware of spoilers!
Name: Ashelia B’nargin Dalmasca (Amalia)
Japanese name: アーシェ・バナルガン・ダルマスカ 『アマリア』
Height: 5’5” (165 cm)
Seiyuu: Mie Sonozaki
Voice Actress: Kari Wahlgren
A princess who had lost everything
The only child of King Raminas and sole heir to the Dalmascan throne, Ashe is believed dead following the invasion. She meets Vaan and the others under the most unlikely of circumstances. Ashe knows all too well she lacks the power to right the wrongs committed against her and her kingdom, but she will not allow herself to admit defeat.
Ashe is introduced in the game’s opening FMV, which depicts her marriage to the prince of Nabradia, Rasler. Unfortunately, he gets killed in battle before the FMV even ends, and her country loses the war. The opening narration proceeds to tell us that Ashe has committed suicide in her grief. As far as character openings go, this is a bit of a downer.
Two years and several hours of playtime later, the player meets a member of the Dalmascan resistance forces by the name of Amalia who looks suspiciously like Ashe. (Spoiler: it’s Ashe.) While she managed to survive the fall of her kingdom, the announcement of her death by her uncle, Marquis Ondore of Bhujerba, and the fact that she lacked proof of her royal status left her no choice but to go into hiding as a member of the resistance. This all comes out after Ashe is captured by the Imperial forces and the rest of the party gets captured with her.
After escaping from the Archadians, Ashe returns to Bhujerba and reconciles with Ondore, who urges her to stay in hiding and wait until the time is right. Of course, Ashe isn’t satisfied with that, and promptly asks the nearest sky pirates (Balthier and Fran) to “steal” her out of her uncle’s custody so she can go find proof of her birth in order to reclaim her throne.
From this point on, Final Fantasy XII is more or less Ashe’s story, and the rest of the cast is just there to support it. As the sole heir of Dalmasca, she alone knows where the Dawn Shard, the last remnant of King Raithwall’s treasures, is hidden: the Tomb of Raithwall, far to the west. Sure enough, they find the Dawn Shard (and an Esper) in the tomb, and Ashe briefly sees a ghostly vision of her late husband, Rasler. As they leave the tomb, they are betrayed by one of Ashe’s fellow resistance members to the Empire, which takes the Dawn Shard and turns it over. The Dawn Shard displays incredible power and takes out an entire fleet, allowing the party to escape.
Ashe has lacked to fight back against the Empire for the past two years. Of course, she has no idea how to use it. She heads south to Jahara and meets with the garif, but they too have no idea how to use it. However, she also meets with the young Larsa Solidor of Archadia, who urges her to set aside her grievances with Archadia in the name of peace for the sake of Dalmasca. While Ashe’s revenge is deep, she agrees to go with him to Mt. Bur-Omisace in order to spare her kingdom another war.
However, when they arrive, they find that the emperor of Archadia is dead, and his much harsher son Vayne has taken his place — negotiations are no longer an option. An envoy from Rozarria, Al-Cid, confirms that war with his country is inevitable unless Vayne is stopped. Ashe sets aside her own succession, and instead seeks the Sword of Kings, which can destroy nethicite like the Dawn Shard and the other treasures Raithwall left, which are now in Archadia’s possession along with manufacted nethicite.
When she obtains the Sword of Kings, however, she decides not to destroy the Dawn Shard when she sees Rasler’s ghost once more. Ashe instead keeps it, uncertain of whether or not she should wield it against her foe despite not having any idea how. Ashe next heads north to Archades by foot to avoid detection, intending to find the Dusk Shard and use the Sword of Kings on it. She goes to the Draklor Laboratory, the home of the Empire’s research, but does not find the Shard there; instead, the head researcher, Dr. Cid, tells her to go to Giruvegan in search of answers.
In Giruvegan, Ashe meets with the Occuria and learns the truth behind the nethicite: the Occuria are a race that have been watching over Ivalice since ancient times and have at certain points given nethicite to special individuals they chose in order to shape the course of history. In the past, they chose Raithwall; in this time, they have chosen Ashe to wield judgment and strike down her enemies. They give her the Treaty-Blade, and tell her to seek out the Sun-Cryst to cut a piece of nethicite for herself.
Following the Occuria’s vague clues leads them to the Pharos and the Sun-Cryst. Ashe approaches the Sun-Cryst, seeing Rasler’s ghost again. She questions whether she should do as the Occuria asked when Judge Gabranth interrupts and urges her to do it, declaring that he slew her father. Ashe rejects the both of them, realizing that if she were to do what the Occuria wanted, she would be no more than a puppet to their will.
Ultimately, the Sun-Cryst is destroyed, and it enables Vayne to take the massive Sky Fortress Bahamut into battle with the Resistance over Rabanastre. The party heads there and defeats him, only narrowly escaping, and afterwards, Ashe declares the war to be over.
A year later, Ashe is queen, with her coronation a month hence. Penelo narrates that she’s grown distant from her friends as a result of her position, as is to be expected. She is shown opening a note from Balthier, who's returned her wedding ring.