The dagger is slightly longer than the palm of a hand, but wide in proportion. It is seemingly made of iron, but appears to also have never been sharpened, with an edge that would not cut much more than butter. The hilt is made of deerhorn and wrapped in gold wire.
Whoever is in possession of the dagger becomes invisible to Shadowspawn, including Myrddraal and Trollocs. Aviendha also states that it is possible that even the Dark One himself may not be able to see its wielder.
The dagger was given to Rand al'Thor by Elayne Trakand shortly before the Last Battle to hide him from the eyes of the Dark One until their very confrontation. He refers to it as Artham and says that attempts to create similar ter'angreal were made during the Age of Legends, but were unsuccessful, and wonders who finally managed it.