Join Date: Jun 2010
Location: New England.....somewhere in that mess of awesomness!!
It is basically a third eye as others here have said, the only notable difference is that it glows a hellish red. If the Navigator/Psyker uses this eye then it will open up, and not any other time. Additionally, according to Lexicanum's Lore at least, it takes quite the mental capacity to simply use the eye; let alone fully utilize it's affective powers.
"Walk Softely, and Carry a Big Gun!"