For those advanced students in Applied Theology, there was a Project which could be attempted. This Project came to be called the God Contest.
Basically, the purpose of the Project was to create a cult which was self sustaining and which was either new or of a different form to the cult it was based on.
Many people attempted the Project but most failed as their creations did not survive for more than a few years. Even the ones who thought they had succeeded showed they had failed when the cults dissolved after the creators died.
Only a few managed to create cults which survived them and gained a place in the Mythology of Glorantha.
Thanatar was successful only to a point as The Creator failed to become integrated into the cult - he did not want to become Thanatarís Neck.
The Three Feathered Rivals was only partially successful as it was not really self-sustaining. The deities were already worshipped shamanically in Prax and there was no need for a new cult. It still survives, though, in Pavis and a few of the tribes.
The Sky Terror (and its relation, a Darkness counterpart which I canít remember the name of, itís in Lords of Terror, though) failed because it became splintered and did not survive as a cult.
Burning Water succeeded too well and the Jrusteli had to reverse its effects to destroy the Firebergs. They then dispersed the cult so that it would not gain its former powers.
The Path of Immanent Mastery succeeded and became a fully-fledged cult. In fact, it succeeded so well that the Kralori State has embraced it as a supported religion, proving that the Dragon Emperors are nothing if not flexible.
Caladra and Aurelion has also succeeded to the extent that it is the Ruling Cult in Caladraland in the Holy Country. This is because the Creators spent time integrating the cult into the relevant mythologies, strengthening and supporting the cult and eventually becoming Cult Heroes themselves.
I have not included Issaries, Lhankor Mhy or Wachaza as I believe they were strengthened in the First Age and were only used by the God Learners. There is no doubt that they used and strengthened the Cult of Issaries, but I think that they merely identified similar myths from a disjointed cult and brought them together.
The Red Goddess was not part of the God Contest, but The Seven Mothers probably used similar techniques and almost certainly knew of the God Contest. Had she been part of the God Contest she would have vindicated all the God Learners' theories.