The One That Binds
This article is specifically about the dimensional binding powers of Tchernobog. For the god himself see Tchernobog.
"Tchernobog is depicted as an evil God in Blood. This is not entirely accurate. In actuality, he is a necessary force in the universe. He is as old as time, and serves as the force that separates the dimensions from one another. Without him all the dimensions would intermingle, and ultimately destroy one another. This force cannot be destroyed, however, in order to perform its duties it must inhabit a physical form that is vulnerable to destruction. It’s original form was destroyed several millennia ago, and since then it has been possessing physical bodies it has come across in order to continue to perform its functions."
--Blood II: The Chosen website
The One that Binds is a title for the god Tchernobog and all his incarnations. It is the title that describes Tchernobog's place in existence: to maintain the thread that holds the realities together.
Before and Early Cabal
It is unknown how the power of dimensional binding came about, although it is presumed that it is as old as time as it is such a necessary power in the universe. It is unknown when the first incarnation of Tchernobog existed, we do know however that its body was eventually destroyed by unknown means and that a second incarnation gained all of its powers and took the task of dimensional maintenance for itself. This practice was continued by several different incarnations throughout history. In order to preserve Tchernobog's powers, the Cabal was founded to create a permanent source of bodies that could be inhabited by future incarnations. This role changed somewhat when the fifth incarnation of Tchernobog took the form of a Buddhist high priest who transformed the Cabal into a religious cult where members performed docile rituals of self control and penance. The Cabal remained religious ever after though in different ways depending on the current incarnation.
The sixteenth incarnation of Tchernobog became an evil, hate-filled man who transformed the Cabal into a dark cult and began to seek out all the powers of existence. He did however continue to do his duty and maintain his job of dimensional repair. As time went on he started to desire the powers of the other realities, and he decided to take drastic measures in order to achieve that power. He cast down Caleb and the other Chosen, his most powerful and loyal servants, in the knowledge that Caleb would return and become the ultimate sacrifice due to the trail of blood he would make while attempting avenge himself and his fallen comrades. With this power Tchernobog would "Open the doors between the worlds and inherit the Earth". However, Caleb's power was under-estimated by Tchernobog and he was destroyed by the very power which he had sought to acquire.
Caleb as "The One that Binds"
When Caleb destroyed the sixteenth incarnation he absorbed all the powers of that god and Caleb himself became The One that Binds. Caleb did not realize he had gained these powers and for a hundred years the thread of the realities began to decay. A powerful being from another realm, the Ancient One, started to invade our reality. During this time the other three Chosen became resurrected from the dead, possibly due to the this decay. They informed Caleb about his powers and warned him that he must use them to close the increasing tears or everything will be destroyed. Caleb scoffed at these warnings and thought that his fellow Chosen were trying to "babysit" him. After a prolonged fight, Caleb eventually manages to destroy the Ancient One and, under Ishmael's guidance, binds the realities and restores the natural order of the universe. It is assumed that he continued to fulfil his role as The One that Binds from that point onward. It is also possible that he eventually officially ascended to become the Seventeenth incarnation of Tchernobog, after bringing the Cabal to heel.