Purviews
Scions buy sequential dots of a Purview just like they do Epic Attributes, including adding automatic successes to any activation roll a Boon requires. The roll for activating a Boon is (Purview + Ability) + Automatic Successes unless noted otherwise in the text of the Boon. When converting existing Boons from other websites, simply replace the Attribute with the Purview.
Your dots of Ability serve as a cap to the number of successes you can gain on any roll or derived value. If you have 5 dots of Death but only 4 dots of Occult, then you would only count as having 4 dots of Death when adding automatic successes to a (Death + Occult) roll.