The name Selene was mentioned by one of the imps that attacked the party. It appears she hired them to assault the group.
When the party met with Master Shen of the comet cult, he appointed Enid’s sister Estra to guide the party to the Earth Shrine. However, once the party made their way outside of Chantilly, Estra lead the party to a trap a revealed herself as Selene, a leader of the Lunatics. As a Changling, she is a master of disguise as well as a formidable spellcaster.