The Anima Mundi is a name given by the gnomes to the life force that exists within all things. It is Latin for "The Soul of the World". It is a byproduct of a balanced ecosystem; the closer to perfection the world is, the stronger the Anima Mundi becomes. In effect it can be seen as created by the Elder Gods who created Gielinor. However, as of late, the Anima Mundi is 'bleeding' and it could well disappear completely (along with the creatures connected to it, such as Vorago and Spirit trees) if the ecosystem is too unbalanced. 
The Anima Mundi is sacred to the gnomes, for they believe Guthix created it when he shaped Gielinor in the First Age. The Anima Mundi seems to be an integral part of the world itself, without which it cannot exist. At the end of the Third Age, the world had been so damaged by the Gielinorian God Wars that the Anima Mundi itself cried out, waking Guthix and prompting him to banish the young gods.
The Anima Mundi is very important to the spirit trees, as they use it not only as a means to survive, but to commune with one another as well. If they are separated from the Anima Mundi, they become weakened and corrupted, and slowly lose their life force until they die.
There have been few throughout the world's history that have attempted to experiment with this force, as doing so is not only dangerous and nearly impossible, but considered an unholy act that goes beyond mere evil. One gnome, Glouphrie, is known to be conducting experiments involving the Anima Mundi within his hidden city, Arposandra. This has allowed him to create large amounts of warped terrorbirds and warped tortoises, among other things.
Players can "briefly feel the power of the anima mundi pass over" them after drinking tears from the Tears of Guthix minigame.
Apparently, interfering with the Anima Mundi creates massive amounts of waste material, as is evident in the Poison Waste in southern Isafdar. It is here that Arposandra dumps the sewage made by its experiments, which slowly destroy more of Isafdar each day. The substance itself is very sticky and full of explosive chemical compounds. It has also made the area's life energy very weak, and nearly caused the death of at least one spirit tree.
The Anima Mundi is known to be able to create very powerful beings, as evident by the existence of Vorago.
- ^ Mod Crow. "Campfire - Answers". 27 June 2013. General Forums.
- ^ Jagex. Official lore livestream with Mod Osborne Official lore livestream, 2 August 2013.
- ^ Spirit tree (Incomitatus), The Path of Glouphrie, RuneScape. "I have lost my connection to the anima mundi. The earth has corrupted my roots and they find only black ichor. My xylem and phloem are tainted, and as a consequence I am alone. [...] Most spirit trees are connected to the anima mundi. She allows us to speak with each other, and she allows passage of those attuned to her from tree to tree. I sense you have travelled the anima."