The spell called "spiritual projection" or "astral projection" brings the caster to the Twisting Nether instead of the Shadowlands; and the Twisting Nether is also referred as "realm of ghosts". However, both planes don't appear to be related, as Outland is floating on the Twisting Nether, but the Shadowlands can be reached in Outland in The Burning Crusade.
Certain playable races will receive new customization options (for example, humans will be able to customize their ethnicities, dwarves and trolls will gain tattoos, and undead will be able to show varying degrees of decay). The Death Knight class (added in Wrath of the Lich King) is being opened up to pandaren (added in Mists of Pandaria) and to all allied races (added in Legion and Battle for Azeroth); players who pre-ordered Shadowlands received access to death knights for these races with the release of Patch 8.3.0, Battle for Azeroth's last major content patch, on January 14, 2020.
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.
But we know that the mission table feature will return in some way, thanks to a Hazzikostas interview with Twitch streamer and professional World of Warcraft tank, Sloot. In the interview, Hazzikostas confirmed that mission tables are present in Shadowlands, and that Blizzard wants it to be something you can do on your phone, rather than a front and center feature. Hazzikostas also stated that the team is looking to evolve the gameplay and offer more for players.
Sylvanas Windrunner, fallen leader of the Horde, has pierced the veil between Azeroth and the realm of the dead, setting in motion a series of events that threatens to upset the cosmic balance between life and death. World of Warcraft players entering the fabled Shadowlands will find the realms of the dead in upheaval. Under the normal order, departed souls were delivered to a realm appropriate to the lives they led, but now, all souls are being funneled into the Maw, where the most wicked are damned to suffer for eternity. As they seek to right the cycle and uncover the extent of Sylvanas' designs, players will forge bonds with the Covenants who hold domain over different planes within the Shadowlands.
During the Burning Legion's third invasion, the Knights of the Ebon Blade traveled to the Shadowlands to acquire the Aggregates of Anguish, five tormented essences of powerful souls - Admiral Proudmoore, Soulbinder Nyami, Grand Empress Shek'zeer, Grand Apothecary Putress and Archmage Arugal. Salanaar required these to conjure the Steeds of the Damned for the order's new Horsemen.