From the publisher:
We are the Mostali. We tend the World Machine. Do not pretend that the world is not broken for we see its mechanism and tell you that its gears are seizing and its connections freezing. Do not dismiss us as greedy capricious fools; we are Mostal's servants and he is The Mover and Maker. We enact his will and make sure the Machine works as it should and flows along the Great River of Time uninterrupted. Without us, all will halt and the Great Darkness shall return. Do not dismiss us as miners and masons: we are the cogs of the world and our secrets and magic as powerful as those of any empire. God Learners - do not seek to steal our secrets and turn them against us. Mostal's tools are made by Mostali and only we know how to wield them properly. Dragon-Men do not take us for ignorant fools: we stare into the heart of the World Machine daily and understand better than you what dragons perceive. Servants of the Thunder God, do not think you own this land; you bear responsibility for what has been broken and must make amends so that it might be repaired. People of Glorantha: know us and hear us. We are the Mostali. We are the World Machine. We are the ground beneath your feet. And it is broken.