On the Inverse Calculus of Unseen Refraction (2012)

From publisher blurb:

The second in our new line of Gothic Grimoires, On the Inverse Calculus of Unseen Refraction takes up the study of the dark side of invisibility. The power to walk unseen is hardly evil in itself, but what unraveling of the mind might occur as it struggles to reconcile the sense that you're not all there. Indeed, what might you do if you didn't have to look yourself in the mirror afterwards? This arcane text delves into invisibility as art and science, illusion and reality. On the Inverse Calculus of Unseen Refraction is an ideal complement to a Gothic Adventure Path or any game where alchemy, magic, and mad science intersect. Featuring a detailed history and description, this tome uncovers new frontiers for alchemical and optical experimentation and creation, including 6 new alchemical discoveries, a new metamagic feat, and 8 new spells and alchemical formulae, ranging from the Transparency Mutagen to vitrific visibility.

Designed by Jason Nelson with the Legendary Games design team of Neil Spicer, Greg A. Vaughan, Clinton J. Boomer, Matt Goodall, Jim Groves, Russ Taylor, and Clark Peterson. Who better to provide you with alternate magical books, spells, and rules for your Adventure Path campaign than the very writers of those adventures themselves? Answer: no one. Legendary Games' Adventure Path Plug-Ins supplement and enrich your campaign experience, offering adventures and supporting products that incorporate and expanding upon unique concepts, themes, and rules subsystems introduced in the Adventure Paths while filling in the background characters, items, and locations that make those adventures come alive in delightful (and often dangerous) detail. Legendary Games combines stellar writing talent with innovative layout and product design and top-notch artistic values that we think will bring you back again and again.

Check out this 8-page gothic-themed magical accessory and Make Your Game Legendary!