The Shadowlands are accessible upon death, where the player-character can roam, and can only be seen by other spirits. The Spirit of Tony Two-Tusk describes the Shadowlands as all grey and dark, swirling clouds. While Uuna was in the Shadowlands, she described it as dark and she was unable to see anything, though she could hear people interacting with her in the physical world. From within the Shadowlands, she could see the light of the naaru A'dal who was in the physical world, but it was so bright that it scared her. The moonlight at Lake Falathim allowed her to see a friend in the physical world.
In previous expansions, entities like the Loa of Death Bwonsamdi, ex-Forsaken Queen Sylvanas Windrunner, and corrupted titan watcher Helya all have spoken of the Shadowlands, and for some, the desire to conquer it. Sylvanas' character arc throughout Battle for Azeroth ends with her seeking to control death itself, indicating that she will play a pivotal role in Shadowlands.
A new army of the dead rises: to combat Sylvanas' assault on Icecrown, Bolvar Fordragon— the revered former paladin who took on the mantle of Lich King to keep the Scourge at bay—has raised heroes from among all the peoples of Azeroth to bolster the Death Knights of Acherus. With Shadowlands, pandaren and all allied races will now be able to become death knights.
Adventurers entering the Shadowlands will find the realm of the dead in disarray. In the natural order of things, souls are sorted and sent on to an afterlife realm appropriate to the lives they lived, but starting around the time of the Burning Legion's third invasion of Azeroth, all souls who have perished—including the innocents slain at Teldrassil—are being funneled directly into the Maw. The Shadowlands are starving for anima even as the Maw continues to grow from the glut of fresh souls. Sylvanas Windrunner has been seemingly perpetrating acts to bring about great amounts of death and destruction. In partnership with the Jailer, they have been working toward a common end for some time.
The popular autobattler mode (games like Teamfight Tactics, Dota Underlords, and Blizzard’s own Hearthstone Battlegrounds) lets players draft units and place them on a chess-like board. The units then battle the units of another player. Between battles, players can buy new units, upgrade existing units, or rearrange them on the board. And according to Shadowlands’ most recent datamine on MMO Champion, World of Warcraft is getting a similar mode.
The origins of the Shadowlands remain uncertain, but they have existed ever since mortal life first arose in the physical universe. They span all worlds, including Azeroth, on which Icecrown serves as an anchor to the Shadowlands. There are those who believe mortal souls are drawn into this dark place when they die, remaining there forever. Others hope their souls will go on to a brighter place rather than languish for eternity within the cold confines of the Shadowlands.