Wild magic is a genetic condition that is a resultant of a mutation of the genetic materials that provide the potentiality to be a magic user or fairy. Even though the great decimation robbed the fairies of their powers, the unique genetic variations that allowed them to perform magic and pass that ability onto their children did not get erased from the world.
Side Note: this does mean that if magic was ever rereleased upon the world that there would be some who would then be able to use the magic powers as the fairies of old.
During the era of the ferry, those born with wild magic were exclusively born of fairies. However it was extremely rare for a fairy inflicted with wild magic was born. While the magic was not in all or nothing condition, but rather a scale.
Those on the lower portion of the wild magic scale could function normally within society and only appeared to have extra power behind the magics that they used. This was often considered as very fortunate as they had more power than their own afflicted counterparts.
Those on the higher portion of the wild magics scale would not be able to function in normal society. Their body had so much power within itself that it could not harness the additional power that came through their body from the cores. Instead of having a little extra boost as the power flowed through them, there was so much power that there was a clogged that prevented all of the magic from flowing through easily. The only way to relieve their symptoms was to teach them to use simple spells that could siphon off there magics into cores. Those suffering from wild magic often did not have similar mental capabilities and frequently found work as assistance to core custodians where there "extra magic" could be used to recharge cores more rapidly. This ability to recharge cores gave them a respectable position within society and they were treated well.
It was believed and hypothesized during the ferry era that those born with low levels of wild magic were considered talented and blessed and extraordinary fairy magic users.
Conversely those on the high end of the wild magic were believed to have been born as a humanized form of "blessed creatures." These blessed creatures of Sagadorm were those that would, when killed or died, would have one of their organs turn into a core. As those inflicted with higher levels of wild magic appeared to have an abundance of energy, they were believed to be "ferry cores" and could produce magic all on their own and without assistance of course.
It was believed that after the removal of all of the ferry magic from sagadorm there were no more people afflicted with wild magic. This turned out to be not the case.
Those with lower levels of wild magic just continued on their normal lives unaware of anything different and unaware of the genetic material they were passing on to their future generations.
Those with higher levels of wild magic suffered similar symptoms of mental anguish and developmental issues as if there was too much electricity in their brain. Since they did not have the ability to release the magic from their body, they were unable to get the relief of draining the magic out of them. They were unable to release their powers into cores as their ancient ancestors. Severe cases left those with high levels of wild magic in a vegetative state due to mental burnout.
How does this relate to Totems of Trilenius?
It could impact those who use the totems. The Totems could temporarily drain the wild magic from those who suffer.