A Water rune is a special type of water rune used during The Slug Menace. It is made by using a blank water rune on the Water altar in the normal way and is used to unlock a mysterious door in the newly discovered shrine beneath Witchaven. Sometimes the blank water rune can break while trying to fuse it with the water altar. In order to unlock the door the player must also have made a special air rune, a special earth rune, a special fire rune, and a special mind rune. Unlike normal water runes, this cannot be used to cast a spell.