In her 20s Teresa was introduced to the "Irish Literary Renaissance" of the early twentieth century, and to Irish music. She was one of the members of the founding board of the Southwest Celtic Music Association in the early 1980s.
Cross became associated with Dianic Wiccans in the Dallas-Fort Worth area, but, disappointed with Wicca, she was curious to learn about the beliefs of her Celtic ancestors. While studying English at the University of Texas in Dallas, she took courses in Linguistics, Mythology and Indo-European comparative mythology. She corresponded with Emmon Bodfish in the 1980s. She started using the Gaelic form of her name: Teresa NicanChrosain.
She was persuaded to write The Sacred Cauldron:Secrets of the Druids using the pen name of Tadhg MacCrossan (which was taken by several reviewers to be a male name). This was the first Celtic Reconstructionist book. It explained the Indo-European origins of Celtic pre-Christian religion. It was criticized for not conforming to the standard feminist pagan lines, and condemned as right wing without any consideration of Cross' actual politics.
She has exchanged ideas with Hindus and Germanicists. Teresa now lives in Fort Worth and is a student of the Vedic and Vedantic literature.
- Tadhg MacCrossan. The Sacred Cauldron: Secrets of the Druids. St. Paul, Minn: Llewellyn, 1991. Review.
- Tadhg MacCrossan. The Truth About the Druids. St. Paul, MN.: Llewellyn Publications, 1993.
- Tadhg MacCrossan. "Neo-Druidism Since the 1700s". Llewellyn Encyclopedia, 16 Jan 2006. http://druuidiacto.forumculture.net/t50-le-neo-druidisme-par-tadhg-maccrossan.
The biography in Amazon (quite likely submitted by MacCrossan herself) is evasive as to when she transitioned. I assume that it must be before she joined Zsuzsanna Budapest’s Diana Wicca which rejects both men and known trans women. (See also Ruth Barrett).
However several reviews and comments on Tadhg’s books are written as if the reviewer takes her to be male.