Brilliant Spell PreperationSource Ultimate Intrigue pg. 79
You have the foresight to prepare just the right spell for the troubles you face.
Prerequisites: Int 13, ability to prepare 3rd-level spells.
Benefit: Select one class for which you prepare spells of 3rd level or higher. Once you select a class, it can’t be changed. When you prepare spells for that class, you can leave one spell slot open as a special slot. The slot must be at least 2 levels lower than the highest-level spell you can cast. You can then prepare a spell in this special open slot as a standard action instead of it taking 15 minutes.
Special: You can take this feat multiple times. Each time you do, you can leave an additional special slot open.