Rudyom in Cove tried to create a way that would enable him to transform Blackrock to other forms. He hadn't much success, however. The wand, as result of his experiments, only made the Blackrock explode, making him see it as a failure.
After the destruction of the Cube Generator in Ultima VII however, the Time Lord told the Avatar the true importance of this device. It was the only way to destroy the Black Gate, ensuring the Guardian couldn't enter Britannia. Retrieving the wand, the Avatar used it to destroy the gate, thus saving all of Britannia.
The wand wasn't seen in Ultima Underworld II; it reappeared in Serpent Isle, but vanished because of a Teleport Storm. When the Avatar found it again in Vasculio's workshop, it had become useless, only making people sneeze. That was the end of this great device for the destruction of Blackrock.