Void

The Seventh Doctor once joked that the first law of space-time travel was to "avoid voids". (PROSE: The Highest Science)

The Thirteenth Doctor determined that the Kasaavin realm was "not really a void". (TV: Spyfall)

According to one account, which admitted to not knowing the full story of the conflict, battles in the Last Great Time War were fought not in physical space, but in the Time Vortex and "even beyond", in the Ultimate Void. For this reason, most of the lesser species knew nothing of the War. (PROSE: Meet the Doctor)

The Tenth Doctor identified the Void as "the space between dimensions". (TV: Army of Ghosts) The Leviathan, a Dæmon spacecraft which launched from Dæmos on a mission to learn if the universe had an edge, encountered an outside force which reduced its speed until it came to stop in a misty white void. The crew went outside to explore, but when Azal went further ahead and vanished, they decided to leave. (COMIC: Voyage to the Edge of the Universe) Whether this void was the Void is unclear.