Sometimes, the spirits roam the Shadowlands without resting. It can be because their resting place wasn't complete, because of a battle in their resting place or because of the corruption of their resting place. To bring eternal peace to the souls, it is needed to destroy the source of corruption or by making a ceremony with items such as [Tuskarr Ritual Object]. A spirit in the Shadowlands can, with enough power over other souls, tear a hole into the living world once they are strong enough. This is how Jin'do returned to Azeroth.
Alpha Beta PTR Vanilla 1.1.0 1.2.0 1.3.0 1.4.0 1.5.0 1.6.0 1.6.1 1.7.0 1.8.0 1.8.4 1.9.0 1.10.0 1.11.0 1.12.0 Burning Crusade 2.0.1 2.0.3 2.0.4 2.1.0 2.1.2 2.2.0 2.3.0 2.4.0 2.4.3 Wrath of the Lich King 3.0.2 3.0.3 3.0.8 3.1.0 3.2.0 3.2.2 3.3.0 3.3.3 Cataclysm 4.0.1 4.0.3a 4.0.6 4.1.0 4.2.0 4.2.2 4.3.0 4.3.2 Mists of Pandaria 5.0.4 5.0.5 5.1.0 5.2.0 5.3.0 5.4.0 5.4.7 Warlords of Draenor 6.0.2 6.0.3 6.1.0 6.2.0 Legion 7.0.3 7.1.0 7.1.5 7.2.0 7.2.5 7.3.0 7.3.5 Battle for Azeroth 8.0.1 8.1.0 8.1.5 8.2.0 8.3.0 Shadowlands 9.0.1
Beings of death are ancient and powerful, and it is dangerous to meddle in their realm. When Odyn peered into the Shadowlands, he saw some of its inhabitants: souls in torment, the husks of the dead, ghostly wraiths with no face, and others with no form, all made of death itself. This was enough to frighten even him. Several races in the Shadowlands, such as the kyrian of Bastion, are souls of deceased mortals who have been transformed to serve a new purpose. If one of these former mortals is killed in the Shadowlands, they die permanently. Other creatures—such as dredgers and stewards—are endemic to the Shadowlands and are naturally born from the magic of death to serve the different realms and help facilitate the process of the afterlife. If one such creature of death is killed, their energy is recycled back into the Shadowlands, and eventually another member of the same race will manifest to take the place of the one that was killed.
After being deposed as Warchief of the Horde in Battle for Azeroth, Sylvanas Windrunner travels to Icecrown Citadel in the Scourge-infested wastes of Northrend, and confronts the reigning Lich King, Bolvar Fordragon. Taking the Lich King's Helm of Domination from him, she tears it in two, shattering the veil between realities and opening a portal to the Shadowlands, Azeroth's afterlife. The Shadowlands have become warped in function during recent times. The Maw, a place in the afterlife reserved for the most sinful souls, is now absorbing all souls.
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.