The ice diamond is one of the four Diamonds of Azzanadra which must be obtained during the Desert Treasure quest. It is obtained from the troll child by defeating Kamil and then freeing his parents from ice.
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, it can be reobtained by speaking to the troll child.
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