Dyfan
Welsh saint
Feast: 14 May (not on the universal Roman calendar; kept in the Roman Martyrology or local calendars)
Who they were
Saint Dyfan is a highly obscure figure who was presumably the namesake of Merthyr Dyfan ("martyrium of Dyfan") and therefore an early Christian saint and martyr in southeastern Wales in Roman or Sub-Roman Britain. He is sometimes styled the protomartyr of Wales. The erection of his martyrium was credited to the 6th-century St Teilo. In the 19th century, Edward Williams conflated him with St Deruvian, a figure in the legendary accounts of the baptism of King Lucius of Britain. The discovery of Williams's alterations and forgeries have since discredited this connection. Partially based on this connection, however, the church of Merthyr Dyfan dates his martyrdom to c. 180.
Summary from Wikipedia (CC BY-SA 4.0), until this page is written up in full.
The miracles
Limited information available on this saint.
Why that counted as sanctity
Limited information available on this saint.