Here's Cyclius, Spirit of Ages:
Cyclius' effect is:
CpS bonus fluctuating between +15% and -15% over time.
and the only thing his placement in Pantheon (Diamond/Ruby/Emerald slot) changes, is how fast that fluctuation cycles (every 3/12/24 hours, respectively).
All other gods directly increase cookie production (CpS/milk/wrinkler bonuses) or enable you to do so (Golden/Wrath cookie bonuses, discounts). However, even looking at Pantheon's page on Cookie Clicker's wikia, the net effect of Cyclius on CpS is 0%.
What am I missing? Is Cyclius supposed to be a god you have to constantly monitor and unslot before negative bonus cycles over?