Select one Vow to be active for Adeptus Astartes units from your army.
Select one combat doctrine at the start of your Command phase. It is active for friendly Adeptus Astartes units with this ability until the start of your next Command phase.
Example: In a battle round, a psyker level 3 Psyker unit could use three psychic level 1 abilities, or one psychic level 1 ability and one psychic level 2 ability, or one psychic level 3 ability.