Quicksilver is the fantasy setting (sourcebook) of the Kingdom of Seloria featuring a bizarre living metal and psychic abilities in a medieval realm with (light) elements of horror.
Written and illustrated by Jeff Dee and Talzhemir and Mike Nystul, it features a fantastic cover painting by Denis Loubet!
[Note: This product is different from Quicksilver Lite, which is a stand-alone game with the same background and non-Pathfinder rules.]