First, we want to make clear that in Fade Rift, magebane is just a combination of mundane alchemical agents and ingredients and some processed lyrium, and has nothing to do with red lyrium. Magebane has been known and used for some time, while red lyrium is a recent discovery, and corrupter agents are used in a wide array of alchemical solutions in the games (and only rumored to be affected by the taint), so it wouldn't make sense for them to be related to red lyrium or otherwise spreading the Blight when used.
In terms of prior examples, Colin will be able to find two references to longterm magebane use.
One is an account of a single individual, a noble-born mage from several ages prior who was apparently fed magebane by her mother from the time she first began showing signs of magic in early childhood. The mother unexpectedly died when the girl was in her late teens without making arrangements for the magebane diet to continue, and a few months after she died, the girl began exhibiting signs of magic again and was taken to a Circle after she accidentally lit a romantic rival's dress on fire during a ball. (The magebane ploy was discovered via the mother's papers by the father in the aftermath of this event and confessed to the Templars etc.) The enchanter who wrote the account taught the girl afterwards and notes that she took a long time after arriving at the Circle to be able to reliably call on her magic, and that when she did successfully do so, it sometimes spiked uncontrollably. The enchanter makes allowances for the possibility that she just wasn't a very good mage, but he also believes that the prolonged repression of her magic during her childhood meant she could not develop the "mental muscles" necessary to control it once she was suddenly in full possession of her power. There's no mention of other physical side effects, but it's also only a short excerpt from a book that's focused specifically on the importance of early intervention with young mages, rather than anything meant to be comprehensive. But there's also no mention of an early death or other tragedy, and apparently neither the girl nor anyone else in the family suspected she was being dosed for the better part of a decade, so non-magical side-effects cannot have been severe.
The second account is more comprehensive, from a Circle that experimented with administering low doses of magebane to a group of post-Harrowing volunteers who weren't too concerned about demons but had difficulty controlling their magic and were interested in just not having to worry about it so much. The mages reported side effects such as mild dehydration and occasional queasiness, especially when they took their doses without food. One wound up with severe stomach ulcers, but was considered to probably be an outlier.
The mages were eventually all phased off of the magebane. Some were phased off as a control group after about a year of use. The remainder were phased off a few at a time as they began exhibiting minor symptoms of mana imbalance, similar to those experienced by mages who overuse processed lyrium to augment their spellcasting. Specifically, at varying times after the one-year mark, despite lacking access to their magic, they began to feel dizziness and sometimes hear voices while awake. The longest a mage lasted without reporting these symptoms was three years, and the author of the study notes a suspicion that the mage actually felt the symptoms earlier but lied about it due to fearing a return to full power. All mages recuperated from the mana imbalance shortly after they stopped taking the magebane, and none had such severe cases that they entered the Fade while awake.
All of the mages, once taken off magebane, took some time to regain access to their abilities. On average it took about a week for every month they had spent participating in the experiment for them to reach their previous power level. (In the study, this was initially considered a positive thing, with some hope that the effect would be permanent, followed by disappointment that it wasn't.) A few of the mages, but not all, reported more difficulty than before with controlling their power level—being unable to cast at some times, or casting spells bigger and more powerful than intended at others—for up to a year afterwards.
no subject
In terms of prior examples, Colin will be able to find two references to longterm magebane use.
One is an account of a single individual, a noble-born mage from several ages prior who was apparently fed magebane by her mother from the time she first began showing signs of magic in early childhood. The mother unexpectedly died when the girl was in her late teens without making arrangements for the magebane diet to continue, and a few months after she died, the girl began exhibiting signs of magic again and was taken to a Circle after she accidentally lit a romantic rival's dress on fire during a ball. (The magebane ploy was discovered via the mother's papers by the father in the aftermath of this event and confessed to the Templars etc.) The enchanter who wrote the account taught the girl afterwards and notes that she took a long time after arriving at the Circle to be able to reliably call on her magic, and that when she did successfully do so, it sometimes spiked uncontrollably. The enchanter makes allowances for the possibility that she just wasn't a very good mage, but he also believes that the prolonged repression of her magic during her childhood meant she could not develop the "mental muscles" necessary to control it once she was suddenly in full possession of her power. There's no mention of other physical side effects, but it's also only a short excerpt from a book that's focused specifically on the importance of early intervention with young mages, rather than anything meant to be comprehensive. But there's also no mention of an early death or other tragedy, and apparently neither the girl nor anyone else in the family suspected she was being dosed for the better part of a decade, so non-magical side-effects cannot have been severe.
The second account is more comprehensive, from a Circle that experimented with administering low doses of magebane to a group of post-Harrowing volunteers who weren't too concerned about demons but had difficulty controlling their magic and were interested in just not having to worry about it so much. The mages reported side effects such as mild dehydration and occasional queasiness, especially when they took their doses without food. One wound up with severe stomach ulcers, but was considered to probably be an outlier.
The mages were eventually all phased off of the magebane. Some were phased off as a control group after about a year of use. The remainder were phased off a few at a time as they began exhibiting minor symptoms of mana imbalance, similar to those experienced by mages who overuse processed lyrium to augment their spellcasting. Specifically, at varying times after the one-year mark, despite lacking access to their magic, they began to feel dizziness and sometimes hear voices while awake. The longest a mage lasted without reporting these symptoms was three years, and the author of the study notes a suspicion that the mage actually felt the symptoms earlier but lied about it due to fearing a return to full power. All mages recuperated from the mana imbalance shortly after they stopped taking the magebane, and none had such severe cases that they entered the Fade while awake.
All of the mages, once taken off magebane, took some time to regain access to their abilities. On average it took about a week for every month they had spent participating in the experiment for them to reach their previous power level. (In the study, this was initially considered a positive thing, with some hope that the effect would be permanent, followed by disappointment that it wasn't.) A few of the mages, but not all, reported more difficulty than before with controlling their power level—being unable to cast at some times, or casting spells bigger and more powerful than intended at others—for up to a year afterwards.