Not much is known about Celestyn, though Thea is apparently close to her, as she is grieved by the thought of forgetting about Celestyn if she drinks from the Cup of Lethe.
When deciding if she should drink from the Cup of Lethe, which will make her a lost witch and allow her to live in peace with her human soulmate, Eric Ross, Thea briefly thinks of Celestyn and how she will have to forget about her. Fortunately, Blaise Harman switched the potion with iced tea, so Thea keeps her memories.
- The name Celestyn is Latin, meaning "heavenly".
- Celestyn is not explicitly mentioned as being a member of the Harman family, nor is she mentioned on the family tree, so it's possible she is related to Thea through her late father, Daniel Avery.
- Spellbinder (mentioned only)