Universal Rule.
If there are at least 3 models with Holy Triumvirate on your Army List and they all have either Caelysian Pantheon or they all have Cult of Errahman, these models can all select spells as follows:
• Wizard Apprentices select from the Learned Spells 1, 2, 3, and 4 of their chosen Path and the Hereditary Spell.
• Wizard Adepts select from the Learned Spells 1, 2, 3, 4, 5, and 6 of their chosen Path and the Hereditary Spell.