Skulls and Shackles
In addition to an astrolabe’s normal +2 circumstance bonus, Svingli’s Eye grants a further +2 competence bonus on Knowledge (geography), Profession (sailor), and Survival
checks when used to navigate on land or sea. Once per day, the user can make a DC 20 Perception check while using Svingli’s Eye as a move action to catch a glimpse of how things really are for 1 round, as if with a true seeing spell. While using the astrolabe’s true seeing ability, the user can also see through concealment caused by smoke or fog and gains a +10 competence bonus on Perception checks to spot hidden or disguised creatures or objects.
Unlike the heavy cast-brass mariner’s astrolabes normally used at sea, this astrolabe is of the more common type found on land (Pathfinder RPG Advanced Player’s Guide 185), made of flat discs of brass. The famed navigator-astrologer Svingli of Morm, a drowned settlement of old Lirgen, was said to have sacrificed her eye to the instrument to grant her knowledge of things beyond mortal sight, thus giving the astrolabe its name.