Oz Vessalius, heir to the Vessalius dukedom, 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, Oz is cast into the prison known as the "Abyss", only to be saved by a "Chain" known as Alice, the Bloodstained Black Rabbit, B-Rabbit for short. 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's Adventures in Wonderland and Through the Looking-Glass and can be considered fantasy and mystery. Pandora Hearts Wiki.

Pandora Hearts (パンドラハーツPandora Hātsu ?) is a manga series by Jun Mochizuki. Originally starting serialization in the shōnen magazine GFantasy published by Square Enix in June 2006. Currently fourteen volumes have been released in Japan. The manga series was licensed for an English language release by Broccoli Books but has been dropped; it has been licensed by Yen Press since then. It has also been made into an anime version, produced by Xebec. On February 11, 2010, NIS America announced it would release the anime of Pandora Hearts in North America. This series also had 9 OVA's (3 minute per episode), which aired from July 24, 2009 to March 25, 2010. Central Wikia


Chains (チェイン Chein?)

Beings from the Abyss that were at one point human, transformed by the Will 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. Some chains, such as Humpty Dumpty, can have multiple contracts. When they do, for each contract it makes, the revolution on an illegal contractor seal will slow down even more.
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, granted the ability never to age the Contractor. In illegal contracts, a clock-like seal appears somewhere on the Contractor's body, 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 imprompt 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, though usually the person is transported forward in time. According to Break, the Abyss can appear as a prison or a broken toy box, depending on the person.
Will of the Abyss (アヴィスの意志Abisu 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 Will of the Abyss is similar to Alice but with white hair. She also dresses in white. Apparently the Will of the Abyss wants Oz to go back in the Abyss, and is revealed to be Alice's twin, although so far it had been unclear in what way they are twins. The Will of Abyss was born in the Abyss at the same time that Alice was born in the human world. The Intention of Abyss hates Alice and wishes to destroy her. It is revealed her real name is Alyss, which is pronounced the same as Alice's name. She's Lacie's daughter who were left into the Abyss, and the human vessel for the power of the Abyss.
The Four Great Dukedoms (四大公爵家Yondai Koushaku Ke?)
It currently consists of the Vessalius, Rainsworth, Nightray and Barma family. These four Dukedoms have been in existence before the Tragedy of Sabrie. 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 behind-the-scenes work.
Before the Tragedy of Sabrie occurred, the Vessalius family was a third class noble family, and thus, not part of the Four Dukedoms. Instead, the fourth Dukedom was the Baskerville house - with Glen as the head. When Jack killed Glen for starting the Tragedy of Sabrie, the Vessalius family was seen as heroes. And thus, the Vessalius substitutes the Baskervilles as the fourth Dukedom. Therefore, the Baskervilles holds the fifth Door to the Abyss.
Pandora (パンドラPandora?)
An organization founded by the Four Dukedoms. It specializes in research regarding the Abyss.
Tragedy of Sabrie (サブリエの悲劇Saburie no Higeki?)
The city of Sabrie 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 Jack Vessalius.
Doors are gates to the Abyss that the Four Dukedoms control. Each Dukedom has control over one, with Baskerville holding the last, fifth Door. It is revealed in Chapter 41 that all along, the door of the Baskerville's was hidden in Sabrie, which is under Pandora's control. Yet, Pandora has never thought to look within to find it.
Blood sealing mirrors
An item used to make a legal contract. Instead of the contractor drinking the blood of the chain, the blood gets absorbed into the mirror where a seal is formed, keeping the seal off of the person. If the mirror is broken, you can lose the contract to the chain. It also has a limit on the power you can use.