Mithridatization is the process by which an individual exposes themselves to low doses of dangerous substances, most often poisons, in order to build up their immunity, so that they can no longer be hurt by the substance. This doesn’t work with all toxins, though, most especially heavy metals, which build up in the body and become more dangerous the more often one is exposed to them. During the days of the Roman Empire, though, it was an effective method of making oneself unpoisonable, since the poisons of which they knew were primarily those to which one cna build an immunity.
The name comes from King Mithridates of Pontus, who so greatly feared being assassinated by poison that he sought to make himself immune to all poisons through Mithridatization. He succeeded too well.
He was defeated by the Roman general Pompey the Great, and in defeat, sought to take his own life in order to avoid being paraded as a trophy through Rome. However, he was unable to poison himself.
In order to kill himself, he attempted to disembowel himself. He was found and stopped by his retainers, though, and stitched up, and all sharp objects were taken from him. Undeterred, in the night he tore out the stitches and removed his own intestines with his bare hands until, finally, he expired.