Iris was a virgin goddess of the sea and sky and the daughter of a marine god named Thaumus and a cloud nymph named Elektra. She was the goddess of the rainbow, a messenger for Olympus (as opposed to her twin sister, Arke who was messenger for the Titans), and a handmaid of Hera. She was believed to replenish the rainclouds with water from the sea. She was beautiful, golden winged, and often indistinguishable from Hebe in artwork. In mythology her role is often taken over by Hermes.
She’s also a minor goddess of justice and makes frequent visits to the Underworld carrying water from the Styx to pour in the eyes of everyone who commits perjury, or collecting items for Hera. She played a role after the events of the Trojan War by disguising herself as a wife of Troy and encouraging the other wives and mothers to set fire to Aeneas’ ships in order to prevent them from leaving Sicily.
According to Ovid, Iris also has the ability to transform mortals into gods with a single touch. She also assisted with Leto’s delivery of Artemis and Apollo by bribing Eiletheyia for her help in giving birth to her children, without allowing Hera to find out. She also helped the Argonauts Zetes and Calais face off against the harpies to protect the prophet Phineus. She convinced the two Argonauts not to kill the harpies in exchange for her promise that the Harpies would not hurt Phineus any longer.
But Iris wasn’t all sunshine and rainbows. She also assisted Hera in cursing Hercules with the madness that caused him to kill his wife and children.