Prerequisites: Alchemist 10.
When you imbibe a mutagen, you become invisible. This invisibility lasts for the duration of the mutagen. The invisibility effect is broken (as normal) if making an attack, but other effects of the mutagen continue for their normal duration. In addition, you can resume invisibility by concentrating for 1 full round.
On the Inverse Calculus of Unseen Refraction © 2012, Legendary Games; Author Jason Nelson.