Cheiron the Satyr

Cheiron was a satyr and an immortal friend of Hercules, who had at one time journeyed alongside Hercules in his adventures.

During one adventure, Hercules mistakenly struck Cheiron with his sword. Due to Hercules' immortal blood, Cheiron was left with a debilitating mortal wound across his stomach and was left in agony, no longer able to adventure. He retired to his home, with his mortal wife Amalthea and two sons.

After many trials searching for a cure, Hercules was able to restore Cheiron's health, as well as make him mortal and human, with the Circle of Fire. (Hercules and the Circle of Fire)

Background information
Although loosely based on the mythological centaur teacher, the mythological Cheiron would later receive a more faithful adaption in the Young Hercules series. Those two characters are necessarily different as, in addition to being two different species, this Cheiron is a fellow adventurer of Hercules' and the other a mentor. It was also heavily implied that the centaur Cheiron was mortal (like other centaurs).