Theiais the Titan of the sun. Theia and Hyperion together represent all the astronomical lights (Theia by day, and Hyperion by night).
During the Titanomachy, Theia was captured by Helios, god of the sun. Rather than kill her, Helios forced her to marry him. Although constantly under Helios’ watch, Theia is sometimes able to subtly influence the world on warm, spring days.