Your Mastery over the arcane arts grants you secret knowledge, allowing you to partake in the following action:

Sammaster's Conjunction. As an action, whenever you cast a spell that requires concentration that is 7th level or lower, you may instead burn a 9th level spell slot and cast two concentration spells instead, either choosing to combine their effects over the same area or to cast them both independently. Likewise, spells casted this way can be upcasted up to 7th level. Both spells and simultaneously at the end of the shorter spell duration or when concentration is dropped.