Original: Baduhennna is solely attested by Tacitus' Annals where Tacitus records that a grove in Frisia was dedicated to her, and that near this grove 900 Roman prisoners were killed in 28 CE.
Simplified: She is only referred to by Tacitus in the "Annals," where he tells of a grove in Frisia that was dedicated to her, near where 900 Roman prisoners were killed in 28 CE.