The Mourner Headquarters serves as the base for the military and strategic activities of the Iorwerthelves during the later part of the Elven Civil War. During this time, access to the headquarters is restricted only to those wearing only full Mourner gear, the standard uniform of a Mourner with rare exceptions. After the defeat of Lord Iorwerth, the successful overthrowing of the Mourners in West Ardougne, and the restoration of Prifddinas, the building no longer serves this purpose.
Prior to Plague's End, as the Mourner Headquarters is fully under the control of the Mourners, who hide their elven identity and their activities from the humans of West Ardougne, only Mourners are allowed into the building. After partial completion of Mourning's End Part I, the player gains access to a set of full Mourner gear, which the player may use to pretend to be a Mourner and thus be permitted to access the Mourner headquarters. From then on until the completion of Plague's End, full Mourner gear is required to access the facility.
The player must wear only Mourner gear to be allowed to enter the Mourner Headquarters, with limited exceptions for additional items that may also be worn. Any forbidden items can be kept in the inventory while entering. Attempting to enter while wearing full Mourner gear along with non-allowed items will result in a Mourner denying you entry, telling you that you should know better than to wear "non-regulation gear"-in other words, prohibited items, and you will be advised to take them off, in order to be allowed to enter. Attempting to enter while wearing only partial Mourner gear, or while wearing no Mourner gear, will cause the Mourners to recognise you as a non-Mourner, to ask who you are, and to ask you to go away.
Once inside the Mourner Headquarters, one can take off any Mourner gear and/or wear forbidden items without being thrown out. You will not be able to enter the trapdoor that leads to the basement without wearing full Mourner gear or while wearing any forbidden items; attempting to do so results in the message "The trapdoor is bolted on the other side." appearing in the chatbox. However, once inside the basement, you can again take off any Mourner gear and/or wear forbidden items without being thrown out. Attempting to talk to the Head Mourner while wearing full Mourner gear with any prohibited items, while wearing only partial Mourner gear, or while not wearing any Mourner gear will result in the Head Mourner recognising you as a human and calling for "Guards!", after which a Level 85 Mourner will come and attack you.