Nashandra is the queen of Drangleic and the final boss of Dark Souls II
Nashandra began her life as the smallest fragment of Manus, Father of the Abyss. After Manus was defeated, he was reborn as various fragments of varying size. Nashandra was the smallest of these fragments, and because of this, was the first to achieve consciousness. Because of her small stature, she began to seek what she did not have; power.
Nashandra travelled to the land of Drangleic where she seduced its king, Vendrick to gain access to the Throne of Want. She warned Vendrick of a looming threat beyond the sea; the Giants. She convinced Vendrick that he must invade their land, and he did so, claiming an artifact of great power. Under the leadership of Vendrick and Nashandra, Drangleic experienced a deep, dark-like peace.
However, the Giants, driven by rage, vengeance and an indomitable will, invaded Drangleic to get their revenge, and to reclaim the artifact Vendrick stole from them. The war lasted for generations, until the Giants were finally driven back, and left the kingdom in ruins. The now ruined kingdom became beset by the Undead Curse. Vendrick desperately toiled to save his kingdom, exiling the undead to far away lands and working to find a cure for the plague. He eventually came to know of Nashandra's true nature, and her manipulation of him. He put into place a series of safeguards to prevent her from reaching the Throne of Want, before departing to the Undead Crypt, a place he was sure she could not follow him to. This left Nashandra the sole ruler of Drangleic.
Dark Souls II
The Bearer of the Curse encounters Nashandra on her throne in Drangleic Castle. She attempts to manipulate the Bearer to open the way to the Throne of Want. She directs him towards the Undead Crypt, suggesting that he put an end to King Vendrick. After this, she will tell the Bearer to follow the "symbol of the king" which will lead him to Aldia's Keep and the Ancient Dragon. Nashandra will warn him that the dragon is no more than a prop and a false deity however, warning him not to listen to its lies yet still urging the Bearer to use the power the dragon gave him to visit the memories of the long dead giants resting in the Forest of Fallen Giants.
Once the Bearer of the Curse has finally cleared the way to the Throne of Want and acquired the means to access it, Nashandra will appear in her true form, and attempt to usurp his quest and claim the throne and its power for herself.
In her human form, Nashandra appears to be a beautiful young woman with blonde hair and an elegant dress. This form bears a striking resemblance to Dusk of Oolacile, a human princess kidnapped by Manus, Father of the Abyss, from whom Nashandra originates.
Nashandra's true form is hideous and terrible to behold. She is a tall, humanoid creature with long, thin limbs. She wears a dress composed of black goo and bones and wields a long scythe in her right hand. Her left hand emanates a purple light, which she uses to conjure her dark magics.