B-Rabbit or Blood-Stained Black Rabbit is a name given to the Chain with the power to sever the Chains of the World due to its supposed nature to turn on its Contractors and kill them. However, unknown to anyone - even Pandora - following the Tragedy of Sablier, other than Jack Vessalius, B-Rabbit is a title given to two individuals within the universe of Jun Mochizuki's Pandora Hearts:
- Oz the B-Rabbit - Oz is the true B-Rabbit, initially a simple Chain that existed as a joint consciousness between two bodies when Lacie brought two black rabbit dolls into the Abyss with her. While one body was destroyed by the darkness of the Abyss when it took on Lacie's memories to deliver to Jack, the other was transformed into a Chain reminiscent of Lacie's Chain, which Jack used to sever the Chains of the World in hopes of plunging the 1st Dimension into the Abyss. Jack was stopped however, and upon attempting to force The Intention of the Abyss into further powering Oz, Alice committed suicide to sever Jack's connection to her sister, possessing Oz's body as her own and reverting Oz to a mere consciousness sleeping within Jack's body that would come to be known as "Oz Vessalius".
- Alice the B-Rabbit previously human, Alice committed suicide to prevent Jack from doing further harm to Oz - then using Jack's connection with Alice's physical body to reach Oz's body as a disembodied soul. Alice then possessed Oz and stole all his powers, casting Oz into slumber as a simple consciousness within Jack's body. Alice then proceeded to attempt to destroy her sister's memories in order to prevent Jack from manipulating her ever again - only to be stopped by The Core of the Abyss. When The Core and Alice's newfound powers clashed, it created an explosion that altered Jack's soul - ultimately making him a reject from the Abyss and forcing him into a constant cycle of growing younger and older all while destroying his consciousness. This did indeed destroy The Intention's memories, but it also scattered Alice's own memories.