The Dark Guardian was the embodiment of chaos in time.
Powers & Weaknesses He was only as powerful as his element in the universe. He was able to change his appearance at will and channel his power of destruction to his follower or followers, like Wrack or The Xhadows. While he was powerful, theoretically, he could do much more damage with the Key/Matrix of Time. In addition, he was unable to enter Michael’s Time Ship, Z’Dun, or the planets Anillon or Vorlan when their defenses were activated and was additionally dispersed by Enlightenment.
History The Dark Guardian played some part in the concept of vampires, seeing their potential as creatures of chaos. He also had part in the concept of the Xhadows. However, he believes the Xhadows “went wrong”. Yet he still considers the Xhadows to be his “bishops” or “knights”. The Dark Guardian, collectively with the other Guardians, removed Prometheus from existence and imprisoned several notable powerful beings. In “Ripos Operation” The White Guardian sent Michael on a quest to find the six segments of the Matrix of Time, transmuted into a variety of forms and scattered across time and space. He warned him of the Black Guardian who would try to prevent the assembly of the Key. The sixth and final segment took the form of a living being. The Dark Guardian used the Shadow to try to prevent Michael and Caesar from re-assembling the Key. After Michael defeated the Shadow and re-assembled the Key, the Dark Guardian posed as the White Guardian and asked for the Key. Observing the Dark Guardian's casual indifference to the life of the living being who died to re-assemble the key, Michael saw through this ruse and scattered the Key through time instead. The Dark Guardian swore revenge on him. Incidentally, the Dark Guardian had some part in organizing Yarven's scheme to restore vampires to power and also had apart in the Xhadows schemes, as seen when the Xhadows are “bishops” in his cosmic chess board. He also had some part in Caesar’s corruption When they were defeated by Michael, he met with the White Guardian and confided that he would need a different method to defeat Michael.(Goth Opera)
The dark guardian created an alternate timeline were he was ruler of the universe and Michael didn't foil his plans. The Earth was invaded by several of Michael's enemies, who fought amongst each other for Earth. This timeline was destroyed when Michael regained the Key/Matrix of Time. (Time & Time Again)