Rituals are extremely powerful, non-location-specific spells that are accessed by having your Cultists work in a Sanctuary. Rituals will require a significant investment of time, mana, gold, sacrifice(s), and/or other items. You may only have your minions prepare a single Ritual at any one time, and once ready it can be held until you wish to use it. You will be unable to begin work on a new ritual until the previous one has been cast.

Rituals are tied to particular Veins of Evil:

Vein of Sloth
Vein of Greed
Vein of Wrath