added by archaeologs
Medusa was one of three sisters born to Phorcys and Ceto known as the Gorgons. According to Hesiod's Theogony, the Gorgons were the sisters of the Graiai and lived in the utmost place towards the night by the Hesperides beyond Oceanus. Later authors such as Herodotus and Pausanias place the Gorgons' abode in Libya. The Gorgon sisters were Sthenno, Euryale, and Medusa; Medusa was mortal while her sisters were immortal.
Beyond the Gorgon's birth, there is little mention of the Gorgons as a group, but Medusa has several myths about her life and death. The most famous of these myths concern her death and demise. In Hesiod's Theogony, he recounts how Perseus cut off the head of Medusa and from her blood sprang Chrysaor and Pegasus, Chrysaor being a golden giant and Pegasus the famous white winged-horse.
https://www.ancient.eu/Medusa/
"Queen." The most famous of the Gorgons. Medusa, who alone of her sisters was mortal, was, according to some legends, at first a beautiful maiden, but her hair was changed into serpents by Athena, in consequence of her having become by Poseidon the mother of Chrysaor and Pegasus, in one of Athena's temples. Her head was now of so fearful an appearance, that every one who looked at it was changed into stone. Hence the great difficulty which Perseus had in killing her; and Athena afterwards placed the head in the center of her shield or breastplate.
There was a tradition at Athens that the head of Medusa was buried under a mound in the Agora. Athena gave to Heracles a lock of Medusa (concealed in an urn), for it had a similar effect upon the beholder as the head itself. When Heracles went out against Lacedaemon he gave the lock of hair to Sterope, the daughter of Cepheus, as a protection of the town of Tegea, as the sight of it would put the enemy to flight.
Usually, Chrysaor and Pegasus are said to have sprung forth from her body when Perseus decapitated her, because at that time she was pregnant by Poseidon.
https://pantheon.org/articles/m/medusa.html