The Shadow Realm

The Shadow Realm is where some of the dead would go.

Origins
Long time ago just after the God Wars Saradomin the God of Goodness created the Shadow Realm. Why? It was so that the dead could roam the land of their own. After the God Wars he could see many restless spirits everywhere, stuck in Gielinor. He felt sorry for them and that is when he created the Shadow Realm.

Location of the Shadow Realm
Local legends say that the Shadow Realm is actually east of Morytania and west of the Tree Gnome Stronghold. The legends are wrong. The Shadow Realm can't be on the east of Morytania because the Eastern Lands are there and the Western Lands are on the west of the tree gnome stronghold. So the truth is that the Shadow Realm is set in a parallel universe of Gielinor where everything is the same except its darker fogier, and its roamed by ghosts.

The Fall of the Shadow Realm
During the early Fourth Age a wizard named Nosaj had a fought with his enemy Wizard Shindor. At that time both wizards were the most powerful wizards that roamed the land the only difference was that Nosaj was a dark wizard serving Zamorak while Shindor was a good wizard serving Saradomin. It was unfortunate for Nosaj to meet Shindor so coincidentally hile Shindor was walking to the Wizards' Tower because this fight would change the history of Gielinor forever. So they fought. It was an intense battle. Both parties were slowly becoming weak. It was a battle between good and evil, magic and ancient magicks. Finally a Saradomin strike struck Nosaj in his heart. He fell on the ground motionless like a rag doll, in a pool of crimson red blood. The next thing Nosaj saw was the dark sky of the shadow realm he was lying on a field. He knew it. He knew he was in the Shadow Realm and he needed to get out of there for revenge. He began experimenting. Decades and decades passed. However one decade in the Spirit Realm is merely a minute in Gielinor. Finally he found way. He coudn't go to Gielinor through the Shadow Realm but he could travel to Gielinor through the runecrafting altars of the shadow (the runecrafting altar located in another dimension. As Saradomin has sealed the Shadow Realm ghosts in the Shadow Realm could not travel to other dimensions. However because the runecrafting altar is not part of the Shadow Realm it was not sealed by saradomin.) When he reached the air altar he casted a spell. Suddely a big portal open out of nowhere. He jumped into it and reached Gielinor. He was a ghost that means even if he dies he would be send into the Shadow Realm and he could travel back to Gielinor through the portal at the runecrafting altar and haunt Shindor. But since that day no-one knew what happened to the two great wizards. Shindor disappeared suddenly the following day the door was opened. Some say Shindor died and both of them are again fighting in another dimension, some say Shindor fleed, some say Shindor just died and is now in the Shadow Realm. We will never know. Because of the portal ghosts could travel to Gielinor and roam it. That is why you can see ghosts at some parts of Gielinor.