UNDOCUMENTED MECHANICS
Lightning Mastery raises your own lightning damage across the board — it is not a bonus for your minions. Skills in this class that benefit: Charged Bolt, Telekinesis, Nova, Lightning, Chain Lightning, Thunder Storm. Their listed damage figures already include Lightning Mastery — every point in it moves those numbers. The game does not list Lightning Mastery under their “Receives Bonuses From”, so the connection is invisible on the skill pages.