Tagg became an apprentice at the age of 16, in 563. He became an adept in 570, and a master-adept in 575, at the age of 28. He had spent most of his time as an adept working with the team that developed mythical creatures, though he was not one of the more prominent members of the team. At that point, his name would not have occurred to anyone as a possible candidate for Grand Sorreter; though no one was expecting Mor to die just one year later, either. However, several months after achieving master-adept status, Tagg conceived of incorporating human intelligence into certain mythical creatures, and diligently worked to figure out a way to do so. By year's end, his efforts had led to the creation of I-Dragons. Several other so-called "semi-intelligent" mythical creatures would be created over the next several years, an innovation made possible by Tagg's work. This qualified him, quite unexpectedly, for the position of Grand Sorreter, which he assumed at the age of only 30.
However, he is also known for being one of the few Grand Sorreters in history to resign the position rather than holding it until his death. In 595, the existence of mythical creatures officially became known to the World Science Council, and then to the public in general, in villages other than just Sorret. Many people in the general public, and especially scientists and reporters, were upset that knowledge of something as important as the creation of new species had been withheld for so long. Some even claimed that if adventurers had known of the existence of such creatures in the wild, deaths might have been avoided. There were, curiously, few complaints from members of The Order, and there has often been speculation that at least some of its members, particularly the Arch-bishop, may have been made aware of mythical creatures' existence at some point prior to this. It does seem the kind of thing, people say, that would have come up at one of the annual Pilgrimages to Monab. However, soon after the public began complaining, Tagg resigned his position, saying that the blame should be placed entirely on Sorreters. Even though he hadn't been the one to conceive of or initiate the creation of mythical creatures, he took the full blame himself, as the current leader of the magical community. He asked that the public not hold either the Sorret Magic Academy or the Council of Magicks responsible, as it was not their decision, but rather that of each of the Grand Sorreters who had been in power since the projects first began in 539, to withhold the information from those outside Sorret. Though he claimed it wasn't a conscious decision to keep it a secret, it was just something that it never occurred to anyone- but should have- to inform outsiders. He never specifically made a statement regarding whether the Arch-bishop or any spirit-talkers outside of Sorret knew of this, though it is strongly implied that they had not been told. However, it is quietly assumed by many that that's not true, and that his resignation, more than an effort to protect Sorreters, was actually an effort to protect the Order.
In spite of this apparent mar on his record, Tagg did not die in disgrace, nor slink away into obscurity. Rather, he moved to First Village, where he became a liaison between the SMA and the WSC. Also, in 598, he published a book called Landian Alchemy, which became quite popular in villages around The Land. He also became an occasional columnist and speaker at various events.