Brenner's Prolonged Permanence

Choose a spell of 5th level of lower than you can cast, and has a duration other than instantaneous, until dispelled or special. You cast that spell--called the prolonged spell--as part of casting Brenner's prolonged permanence, expending spell slots and material components for both. The casting time for Brenner's prolonged permanence is twice that of the prolonged spell.

Once cast, the duration of the prolonged spell is doubled. Alternatively, if the spell has the ability to become permanent after a certain number of castings, such as teleportation circle, the number of castings the prolonged spell counts towards is doubled.

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the effects on the prolonged spell are doubled an additional time for each slot above the 6th (four times for 7th level, eight times for 8th level, and sixteen times for 9th level)