Gods arise from life.
All gods were once living creatures that reached the pinnacle of their species (by whatever metric that is measured) and then, due to the accumulation of Titanic power and its tendency to form true awareness, ascended to something 'more'.
A little-known fact is that Gods are limited to their world of origin, unable to travel the Ways.
All species have the potential for spontaneous ascension. However, the rate of occurrence is extremely rare. The exception is the mammalian species that evolved on the world of Midgard. On this world, the so-called 'dragon gods' took it upon themselves to manipulate the natural process to ensure that awareness would manifest in mortal creatures. Their reasoning was that an aware species could work to stave off both Celestial incursion and random events. As a side effect of this process, the number of gods rising from the mammalian lines has increased exponentially.
Godhood can also be forced by Arcane means.
Ahman, Bast, The Bull, Dragon Gods, The Green, Hades, Serpent Child, Skittering One, Zeus (of Olympus)