Marta was a habitant of a town called Christmas. She was coupled with Abramal. She told The Doctor and Clara Oswald about the Truth field.
When asked if they liked the Truth field, Marta said "Yes" the same time as Abramal said "No". This could be seen as a married couple joke. TV:The Time of the Doctor
Appearance
She had 19th century-styled clothes. She looked about 50-70 years old.