Creeping Wither

Being overexposed to mana, can not only bolster you magical capabilities, but might also, if one is unlucky, inflict a dangerous sickness. Being first discovered by slaves suddenly showing signs of developing sicknesses that typically only appear at an old age, like brittle bones, constant pain, cramps, forgetfullness or their skin and hair loosing color, made scholars wonder why all of a sudden some individuals seem to age at a very accelerated age. These conditions were only found in slaves who were working in the Pyrus-Crystals mines, which is why it was first assumed, that these mines must be contaminated with some sort of gas or fungus that caused this illness. However, scholars who heavily studied these crystals would also soon display the same health problems.
After experimentation it was found, that it was not the mines, nor the crystals themselves, but the mana they emmit that cause this condition. No matter what animal, when exposed to this energy for long enough, they would start to age at a rapid pace, quartering their life expectancy.
As these crystals were critical to the airships, countermeasures had to be found to shield people from these effects. First, mana absorbing potions were used as a temporary treatment, effectively reducing the amount of mana that existed in a persons body at any given time. This was not satisfactory however, since among the afflicted were royalty and wealthy merchants who desperately needed a treatment that would not simply halt the effect, but to revert it.
In an effort to find such medicine, multiple expeditions were launched until one returned with promising findings. They had found an animal which would not die of natural causes, their blood having the ability to halt and revert the effect of aging, with hormones keeping it steady so the beast would simply remain a certain age.
Mixing it's blood with mana absorbing potions finally netted the desired result. When injected into a patient, the illnesses effects would revert, bringing the person back the the bodily age the were supposed to be at.