An act of magic in Glorantha is an exchange of energies between mortal and myth. The mythic world includes the gross intangibles, such as the Platonic ideals or conceptions such as Love, Art, etc. These are often understood and defined as deities. Whenever someone draws upon that Force (or deity) it is an act of magic and each time someone does something for that mythic ideal it is an act of magic.
This mutual system of interdependence is the source of the magic in the world of Glorantha. The very fiber of the world is steeped with myth, and a general awareness of the newness of the world is close at hand. People are glad to give sacrifices and promises to their deities and deities are happy to help their worshipers. The pathways between either are wide and easy, and the Power flows easily.
The myths of the world are, by their very nature static and present a relatively fix aspect in all pre-determined actions. That is if a deity once performed an act, they would always perform that act in the same way. If mortals also perform the act inn the same way, they would partake of the divine Power of the act, and the exchange of power would be a magical exchange.
When performing new actions, the deities are more liberal in their actions, but the more powerful a deity is, the more restrictions are placed upon it. No deity is capable of performing an independent act and still maintain their security of eternal immortality. The possession of free will necessitates the threat of mortality. And given the decision, almost all deities would prefer to maintain their current status than risk change. Too much change and Chaos could again enter the world and devour even immortality.
But mortals, who approach magic from the world of free world, change, and development, are capable of changing the world of magic, even to the extent of altering the face of myth and entering the immortal realms.
Are Runes also “gross intangibles”?
depends on the Rune. Elemental Runes are the archetypes of that element. Power Runes are gross intangibles. Condition Runes are states off being.
The Runes are a key way of understanding the cosmos, but there are things that are also key that are rarely expressed as a Rune – the Twins, etc.