~The World Guardian, Tuska, and the Edicts *
As I said before, God’s perform magic by creating ripples in the Anima around them, making them effectively as Guthix would describe them as very agents of imbalance- as the very magic they used relied on creating a slight imbalance in the Anima Mundi.
Guthix used his power to alter our own Animus- making us agents of balance- our soul has the power to smooth out the ripples in the Anima Mundi created by the gods, should we choose to let it. We can cancel out their magic by Calming the Anima around us. That being said- we cannot completely dissipate the waves of magic sent our way by the gods- should they try hard enough, they can reach us.
“It is true. Thanks to the protection of Guthix... I cannot teleport you against your will, and much of my power seems ineffective against you.” – Saradomin, Doc.
Guthix was trying to pull the same trick with the entire world, making it impossible for the gods to even open a way into this world, unable to bore into the outermost of the Anima Mundi- but such a feat required constant attention, for the Anima Mundi’s soul is far more expansive then our own, and he lacked the needed power to permanently alter it. So, upon his death, the world could no longer cancel out God Magic on its own- allowing gods to once again enter this world.
Then there’s Tuska. Tuska didn't so much create a barrier- as she did destroy a world. Tuska managed to devour a world- but I imagine most of the Anima of said world she was unable to absorb most of it- like a child slamming their head into a cake, rather than eat it piece by piece. So- the Anima surrounding her isn’t balanced- but rather completely unstable. The Gods cannot get near her- for similar but opposite reasoning than why they couldn’t get into Gielinor. The Anima surrounding her is like a rapid torrent, constantly shifting, they are unable to calm it enough to enter or manipulate it.
"We call it being a hero"
"That's interesting, we call it utter stupidity"