From time to time, it is worth bringing some material you likely already have to your attention – here’s an explanation of what Gloranthan magic is from the RuneQuest Roleplaying in Glorantha core rules:
To grossly oversimplify, Gloranthan magic is the interaction of mortals existing within Time with the timeless and eternal powers of the God Time. In the God Time, there was no division between the worlds of men and gods, between life and death, or body and spirit. The Gods War introduced the power of Death, which separated all with violence, death, and entropy. War entered the world and the endless beauty and harmony of the universe was destroyed. Reality was fractured. The eternal gods themselves would have ceased to exist but for the Cosmic Compromise, whereby the gods that still existed abdicated their free will within the temporal world voluntarily, rather than lose their All into the maws of nonexistence. The gods remained eternal, at the cost of being restricted henceforth to only the deeds they had performed during the God Time, which are now fixed and unchanging in the world of Time. If the gods were ever to transgress their fixed and allocated positions in the Cosmos, they would enter the shifting world of Time and would be destroyed by Death and entropy.
Mortals exist within Time. The necessity of Death in the world of Time is another result of the Cosmic Compromise. Mortals are separated from the gods, are subject to both Life and Death, and upon death their spirits are separated from their physical bodies.The dualistic worlds of eternal God Time and mortal Time are the basic polarities of Glorantha. From these opposing poles comes all known reality. Magic is the result of the interaction of these two worlds; drawing upon the timeless and eternal God Time to affect the mortal world of Time. With magic, a priest of Orlanth can call down thunderbolts from the sky, a Praxian warrior might call upon a spirit to guide his arrow true, or a sorcerer might command the waters to seize and capsize an enemy trireme.