Oz Vessalius, heir to one of the duke houses, has just turned fifteen. His life is rich and carefree, darkened only by the constant absence of his father. At his coming-of-age ceremony, however, everything changes. For no reason that he can discern, he's cast into the prison known as the "Abyss", only to be saved by a "chain" known as Alice, the bloodstained black rabbit. The mystery there begins as Oz unravels the mystery behind Alice, the Abyss and the strange organization known as Pandora. The series features heavy references to Lewis Carroll's "Alice in Wonderland" and can be considered both fantasy and mystery.
- Chains (チェイン Chein?)
Beings from the Abyss that were at one point, human, transformed by the Intention of the Abyss. They must sign a contract with a human contractor in order to leave the Abyss. Chains involved in illegal contracts must repeatedly consume humans in order to gain power.
- Contract (契約 Keiyaku?)
An agreement between a chain and a contractor. The chain is bound within the contractor and can be called out at will. In return, the contractor provides passage for the chain out of the Abyss. Legal contracts that were made possible by Pandora have been granted the ability to never age to the Contractor. In illegal contracts, a clock-like seal appears on the contractor's chest, over their heart. Each time the chain's powers are drawn, the hand in the seal moves like on a clock. Once the hand makes one full rotation, both the contractor and the chain are dragged into the deepest level of the Abyss.
- Contractor (契約者 Keiyakusha?)
A human who makes a contract with a chain. There are certain procedures to making a contract, but impromptu contracts can also be made, although they are illegal.
- Abyss (アヴィス Avisu?)
The world that chains come from. It exists in a different dimension as the world, and as thus, time doesn't truly exist in the Abyss. A person can find themselves in any random time period upon exiting the Abyss. According to Break, the Abyss can appear as a prison or a broken toy box, depending on the person.
- Intention of the Abyss (アヴィスの意志 Avisu no Ishi?)
The existence that governs the Abyss. Usually appears in the form of a bloodied rabbit doll with big round eyes. The real form of the Intention of the Abyss is Alice with white hair. Apparently the Intention of the Abyss wants Oz and Alice to go back in the Abyss. The Intention of the Abyss and Alice are somehow connected. At the same time, the Intention of Abyss is born in the Abyss, while Alice was born in the human world; It is soon figured out that they are twins.
- Four Great Duke Houses (四大公爵家 Yondai Koushaku Ke?)
It currently consists of the Vessalius, Rainsworth, Nightray and Barma family. These four houses have been in existence before the Tragedy of Sabrié. They founded the Pandora and each hold chains and a door to the Abyss. Of these four houses, the Vessalius and Nightray houses are thought of as exact opposites, like light and dark: the Vessalius house works publicly, while the Nightray house is responsible for doing the backstage work.
Before the Tragedy of Sabrié occurred, the Vessalius family was only a third class noble family, and thus, not part of the four duke houses. Instead, the fourth house was the Baskerville house - with Glen as the head. When Jack killed Glen for starting the Tragedy of Sabrié, the Vessalius family were seen as heros. And thus, the Vessalius substitute the Baskervilles, as the fourth duke house. Therefore, the Baskervilles holds the fifth door to the abyss.
- Pandora (パンドラ Pandora?)
An organization founded by the four duke houses. It specializes in research regarding the Abyss.
- Tragedy of Sabrié (サブリエの悲劇 Saburie no Higeki?)
The city of Sabrié was once the capital city of the world. However, 100 years ago, for unknown reasons, Glen Baskerville used a ritual to send the entire city, with its citizens, into the Abyss. Glen was then supposedly killed by the four duke houses.
- Doors
Doors are gates to the Abyss that the four duke houses control. Each house has control over one, with Baskerville holding the last, fifth Door.
Oz Vessalius (
オズ ベザリウス Ozu Bezariusu?)
The main character of the story. A 15 years old boy with blond hair and green eyes from the prestigious Vessalius family, whose father is the reigning lord. His mother was killed by the Nightray family, but despite this, he retains a bright, optimistic, and energetic personality. The story of Pandora Hearts starts when Oz turns fifteen. During the ceremony to celebrate this reaching of adulthood, he was dragged into the Abyss for the sin of 'existing'. There he meets the chain named Alice and makes a contract with her. Upon returning to the real world, he finds out that 10 years have passed. In order to find out what his sin meant, he began to work under Break as part of Pandora. During this, it is shown that when he was young, he worked hard to gain praise and recognition from his father. However, he had discovered that his father hated him to the point of not wanting to touch him. After experiencing this, Oz began to think that there is no guaranteed thing in the world. He thought of himself as weak and, in order to protect people, he should at least remain an obedient child and let harm come his way.