This piece from the Mythology book is among my absolute favorite conceptual pieces. It shows somewhere in the vicinity of a hundred deities, some with cults, many without. Imagine these as the main architects of Glorantha. Their dances, squabbles, and conflicts create the world our characters inhabit. There are of course many smaller entities, perhaps local heroes or scraps or devolutions of one of these deities, but this is the basic contours that pretty much everyone can identify.
Different cultures have different names for many of these gods, different representations, and some are ignored while others are divided into multiples, but wherever you go in Glorantha, you can find this framework if you squint hard enough.