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unfortunately, need to requisition a new Sensor from your Institute. Also, there is a tremendous quantity of demonic energy in your immediate vicinity. You must make sure to evaluate your immediate circumstances before trying to examine your Sensor; it is possible that you are about to be devoured by either a Greater Demon or a Portal to Hell.
    So if you had a human who’d drunk a lot of Greater Demon blood when he was a baby, would he set off a Sensor?
    Who would do such a terrible thing.
    Just hypothetically.
    If you already know this guy, track him down! Sensors are for demons you don’t already know personally!
    God, get a room, you two.
    Good point.

THE STELE
The stele (pronounced in English 'steh•lay ) is listed here among the tools of the Shadowhunter but could just as easily be mentioned among weaponry; it is the fundamental tool of the Nephilim, the device by which Marks, our only magic, may be inscribed. An elaborate decorated stele is often the first tool given to a young Shadowhunter at the beginning of her studies.
The stele is a wandlike instrument, made of pure adamas . It is inert when not in use but when taken up glows and warms with the magic of the Marks. It is longer than modern writing instruments, usually a foot long or more, and as a result contemporary Shadowhunters will require practice to be able to draw runes with facility when using one.
All steles are functionally identical, but of course there is wide variation in their design. Many have handles inscribed with family crests and the like, some are studded with gems—the only requirement for a working stele is that it include an unbroken rod of adamas of at least a certain length. On the other end of the spectrum are the narrow practice steles given to child Nephilim to learn runic manuscription on sheets of parchment.
The first stele is believed to have been a rough oblong of adamas used by Jonathan Shadowhunter to inscribe the first Marks on his own skin. The stele designs have become refined over the years. Some scholars see a link between the stele and the Jewish yad , the ritual pointer used to avoid physically handling the parchment of the Torah when reading from it, but no direct connection can be made, although it is probable that the earliest Iron Sisters were inspired by such designs. Represent!
Demons are not harmed by exposure to a stele, but they will typically recoil from one, as they will recoil from all adamas .
WITCHLIGHT STONES
One of the great secrets kept by the Iron Sisters is the precise manner by which adamas is extracted and purified from its ore. What we do know, however, is that the presence of adamas affects the rock from which it is extracted, and though it is simple rock, it gives off a pure white glow, as though reflecting the light inherent in the adamas . These “sister stones” of adamas are broken up and polished by Iron Sisters, and Marked to make their glow a property that can be turned on and off at the will of the Shadowhunter holding them. Most rune-stones are basic and interchangeable, and rarely do Shadowhunters get attached to a particular stone over any other. All Shadowhunters carry a witchlight stone, to remind them that light can be found even among the darkest shadows, and also to supply them with actual light when they are themselves literally among dark shadows.
The great advantage of witchlight stones is that their glow never fades or dissipates, for no fuel is being consumed in creating their light. Such a stone can, however, be destroyed by pulverizingit into dust, whereupon the angelic light absorbed into it will dissipate; thus one never finds “witchlight sand” or the like.
The largest single witchlight crystal in the world can be found in the Silent City in the form of the Angelic Colossus, a representation of the Triptych, the familiar motif of Raziel ascending from the water wielding the Mortal Instruments. The crystal stands roughly thirty feet tall, and it guards (and lights) the