Pre-universe

The Pre-Universe was the universe which came before this one. After the destruction of the Pre-Universe, some species found their way into this universe, and some (such as the Old Ones) ended up with god-like powers. (NA: All-Consuming Fire, MA: Millennial Rites)

It had a green void, stars shaped like doughnuts and physical laws closer to what might be understood as magic. (MA: Millennial Rites).

Knowledge of this universe was a closely guarded secret, and was only in the Doctor's possession as a result of his connection to the Matrix during his time as Lord President (MA: Millennial Rites, DW: The Invasion of Time). Even then, the knowledge would ultimately prove temporary; In his Sixth and seventh life the Doctor was fully conversant with the details and specifics of this universe (NA: All-Consuming Fire, PDA: Synthespians™), whereas by his tenth it would almost be an article of religious faith to him that such a universe could not have existed (DW: The Impossible Planet).

The Beast claimed to have originated before the universe, as well as to have been imprisoned by the Disciples of the Light, likely placing both in the Pre-Universe. (DW: The Impossible Planet / The Satan Pit).

Abaddon, being the son of the Beast, probably also came from this period and was imprisoned around this time. (TW: End of Days)