Tegfedd ach Amwn Ddu

Who they were

Tegfedd (6th cent.), sister of Tydecho, whom she accompanied to Wales.

The miracles

There was never a formal cause: she has been honoured as a saint since before the Church's formal processes began.

Why that counted as sanctity

Stanton's Menology of England and Wales (1887) names her in its list of other Welsh saints, many of whom, it says, were probably never in fact honoured as saints.