According to Hopespear, the Plain of Mud is an area just north of East Ardougne, where there was once a great battle fought between different tribes of goblins. It is so called because during the days the battle raged, it rained constantly, causing the ground to become very muddy. One night during the battle, Hopespear had a dream and Big High War God told him that the fighting must stop, and that one day, the Chosen Commander would come to lead the goblins to victory. He told the generals who stopped fighting, and decided to build a temple, which sank into the mud, so they made it a secret underground temple. The temple is now accessible via the Goblin Cave. Players can teleport to the area using a Plain of Mud Sphere.
After a player completes the quest Goblin Diplomacy, goblins will talk about the Plain of Mud. They usually say: "Goblin century mark year of big battle on plain of mud. That when Big High War God give us commandments!"
The commandments are:
- Slay enemies of Big High War God.
- Not show mercy. Not run from battle.
- Not doubt word of Big High War God.
When a player asks: "Where are the plains of mud?", a goblin may reply " That goblin secret! No human ever find plain of mud!" and then attacks the player.
During the Land of the Goblins quest, the player finds out that the Plain of Mud is located near the Fishing Guild and that there is a temple hidden underneath the surface. The ghost of Hopespear, located in the catacombs of the temple, tells the player about the significance of the Plain of Mud.