For the group leader, see Head mourner.
Mourners are the "plague healers" of East and West Ardougne. They are in part the subject of the Sheep Herder, Plague City, and Biohazard quests, and are located mostly inside West Ardougne and around its walls inside East Ardougne. They are led by the Head mourner.
Shortly after release, mourners were the subject of a bug, or perhaps oversight, where they were
attackable and gave a lot of experience despite having very low hits. This was abused by many notable players to obtain experience abnormally quickly. 
This article on a
non-player character has an associated dialogue page.
Drops (level 22)
Bones & coins only drop if the player does not have the bronze key in their inventory.
Bronze key is automatically added to the player's inventory and can only be gotten if player does not already have one in their inventory.
Drops (level 25)
The level 22 Mourner will only give experience when players kill him with a bronze key in their inventory.