Good point, not all Knowledges were written as clearly as they should be.
Cult grants you Blessings, which are special powers that are accessible from the third item slot.
Without Cult, this slot is disabled.
With Cult unlocked, you can now assign Blessings to your followers.
They cost 2500 Power Points to cast, and add 5 to the value of a specific skill.
Cosmos allows you to build the Sacred Totem.
Once built, you can assign up to three followers to a Totem. Their combined speed values will apply to a specific dance, improving Devotion (Power Point production), Resource production, Attack or Fertility.
You also gain access to a Mass Healing power: heal every follower in the village for 6000 Power Points.