Throne of Want

The final hall beyond the King's Ring door near King's Gate.

Bosses

Throne Watcher and Throne Defender: They revive each other, so bring both down at roughly the same time.
Nashandra: Destroy the small curse statues she summons and attack her legs.
Aldia, Scholar of the First Sin: Unlocks the second ending; dodge his fire waves and root attacks. No souls or items.

Ring of Blades+2: Dropped by one of the two Pursuers in the Drangleic Castle throne room at intensity 2+; grab it before dying.
Ring of the Evil Eye+2: Dropped by the Throne Watcher and Defender at bonfire intensity 2+.
Soul of Nashandra: Defeat Nashandra at the Throne of Want.
Throne Defender Soul: Defeat the Throne Watcher and Throne Defender at the Throne of Want.
Throne Watcher Soul: Defeat the Throne Watcher and Throne Defender at the Throne of Want.

From King's Gate go out and down to the left and open the door with the King's Ring
Talk to the Emerald Herald and follow the path to the fog
Defeat the Throne Watcher and Throne Defender; summon Benhart of Jugo (left) or Head of Vengarl (right). Reward: Throne Watcher Soul, Throne Defender Soul and 68,000 souls
Nashandra appears only if the Giant Lord is dead; defeat her with your summons. Reward: Soul of Nashandra and 90,000 souls
Then defeat Aldia, Scholar of the First Sin; no reward, but it opens the second ending
Sit on the throne or walk away to choose your ending (The Heir)
You return to Majula to finish up before starting the next cycle
NG+: the Throne Watcher and Throne Defender also drop the Ring of the Evil Eye+2