Complex sentence: Lady Gwen Thompson (September 16,1928--May 22,1986) was the pseudonym of Phyllis Thompson, author and teacher of traditionalist initiatory witchcraft through her own organisation, the New England Covens of Traditionalist Witches.
Split into simpler sentences: Lady Gwen Thompson (September 16,1928--May 22,1986) was the pseudonym of witchcraft author Phyllis Thompson. She taught traditionalist initiatory witchcraft through her own organisation, the New England Covens of Traditionalist Witches.