mythic background:
Jason: son of
Aeson, nephew of
Pelias > kingship of Thessaly > quest of Jason &
Argonauts (e.g. Hercules, Orpheus, Peleus)
for Golden Fleece in Colchis (trials?)
Medea: daughter of
Aeetes (King of Colchis), granddaughter of the Sun/Helios, brother of
Apsyrtus; her powers (Aeson vs. Pelias)?
Corinth & the aftermath (Seneca's play):
King Creon & his daughter (Creusa) = protective alliance against threat of Pelias's son
Acastus

Medea and Pelias, late 5th century pyxis