Nessos, the son of Ixion and Nephele, was a centaur who acted like a ferryman in the River Evinos, carrying pedestrians across the river on his back. Nessos was known to have a bad relationship with the Greek hero Heracles.
One day Heracles came to the river with Deianeira, his third wife. Heracles was strong and could cross the river all by himself, but he entrusted his wife to Nessus to get her across. However, Nessus tried to kidnap (or rape) Deianeira, and Heracles killed the centaur with arrows dipped in poison.
Before he died, Nessos managed to give Deianeira a love potion mixed with his blood and semen, and told her to soak a robe of Hercules in it so he would never be unfaithful to her again. This filter eventually burned the great Greek mythical hero, Heracles fatally with terrible pain.