Cate Tiernan is the author of the Sweep series (known as Wicca in the UK), the Balefire series, and the first book of the Immortal Beloved trilogy by the same name. The second book of the series is due to come out in 2011.
She writes under a pseudonym. Her website is here.
Her works contain examples of:
- Always Identical Twins: In Balefire
- No Export for You: Balefire was only published in the US and Denmark, though that may have changed since.
- Immortality Immorality: It's implied that most immortals are this at some point- forever, it seems, is more than long enough to get bored with being nice.
- Magick: In all three series.
- Secret Legacy: Cate Tiernan seems to like this trope an awful lot...
- Witch Species: Both Wicca and Balefire are centred around people who are born witches.