You can convert any spell into an invisible veil.
Prerequisite: Spell Focus (Illusion), Arcane spellcaster, caster level 9th
Benefit: As a standard action, you can sacrifice a prepared spell or unused spell slot of 1st level or higher and transform it into a transparent veil, granting yourself invisibility, as the spell. This invisibility lasts for 2 rounds for every level of the spell or spell slot you sacrificed. Once the invisibility ends (for any reason), you cannot use this feat again for 1 minute.
Path of Shadows, © 2015, Ascension Games, LLC; Author Christopher Moore