The Timeless Void, also called the Outer Dark, the Everlasting Dark or the Ancient Darkness (Q."Avakúma", "Oiakúma", "Kúma") was the dark realm ouside of Arda and the Timeless Halls.It was a region of nonexistence outside Time and Creation where the Essence was absent.
Morgoth had long wandered the Void before he had entered Arda and was banished there by the Valar after the War of Wrath.Ungolianth had been a dweller of the Void he had met and befriended her as well as possibly other Demons of the Void.
The empty space outside of Arda was sometimes known as the "Inner Void" (Q."Mikúma" or "Lusta") , but the Wise knew that this part of Eä was different from the Ancient Darkness outside the Timeless Halls.