The shadow leviathan is a wyrm that lives in the deep 'shadow' of the Shadow Realm, where even Gods may find it hard to traverse.[1][2][3] It was first mentioned by an unknown dragonkin in The Shadow Realm. He describes the wyrm as being large enough to wrap around whole worlds and having a need to hunt any sources of light that it finds, but would die if it left its natural habitat.
It may have been referenced in The Promised Gift, though it is possible that it was a general array of powerful creatures living in the deep 'shadow'.
The Fremennik entity Jormungor is thematically described to be very similar to the shadow leviathan, described as a wyrm that wraps around the planet and having a hatred of all other living things.
- ^ The Shadow Realm, RuneScape. "It is possible to navigate the rivers of this interplanetary network, but as one travels lower into the universe, the shadows become thicker and denser... Beyond Freneskae at the utter end of the universe are the true depths, where the realm grows thicker and darker still, such that even gods must turn back."
- ^ The Shadow Realm, RuneScape. "Just as the abyss and void hold their own forms of life, so too does the shadow, and such beings can be found occasionally in these shadow seas, far from a world's surface. They are twisted and elusive creatures, more formless than definite. They are suffused utterly with shadow energy, composed I believe of the same matter as the sea they swim in. While within their realm they are quite invisible from beyond it, and when brought forth into real space, they expire rapidly."
- ^ The Shadow Realm, RuneScape. "The shadow leviathan, a great wyrm large enough to coil around worlds. It hunts through the dark, seeking any pinprick of light to devour. If it has a mind, it knows only hatred of the living. Planes not filled with the shadow cannot sustain its bulk, and so seem safe from its predations."
