It is recommended that players deposit Diamonds of Azzanadra in the bank as soon as they obtain them, as a level 81 stranger may appear and attack anyone holding one of these gems. Each additional diamond in one's inventory increases the likelihood of being attacked.
If you lose your diamond you can find another in the spot that you killed Damis. It will give a message saying, "The Diamond of Shadow seems to have mystically found its way back here..."
According to Trindine's logs, the shadow diamond is actually the soul gem of a long deceased Mahjarrat particularly skilled in shadow magic, which was disguised as a gem to mask its true nature. It has the ability to corrupt those who carry it, although they can resist it if they are strong-willed and are not distracted by outside influences. She entrusted it to one of her praetorian guards, Titus, to bring it to Azzanadra.
This diamond was formerly known as the "shadow diamond", then was changed to the "rock diamond", and then back to its current name.
If you would like a duplicate of this diamond, you can get one. Drop your diamond in the area you defeated Damis, and then hop worlds. Pick up the diamond in the new world, and then hop back to the old world and pick the first diamond back up.