The Scotish Plaid Kilt Company Feast of St. Filian, August 26

It appears he really existed, but the legends are some of the best. From Wikipedia:

Saint Fillan, Filan, Phillan, Fáelán (Old Irish) or Faolan (modern Gaelic) is the name of (probably) two Scottish saints, of Irish origin. The career of a historic individual lies behind at least one of these saints (fl. 8th century), but much of the tradition surrounding 'Fillan' seems to be of a purely legendary character.

 St. Fillan was credited with powers such as the healing of the sick and also possessed a luminous glow from his left arm which he used to study and write Sacred Scriptures in the dark

 

 The Mayne was an arm bone, now lost, enclosed in a silver reliquary or casket. Legend has it that King Robert the Bruce requested the bone be brought to the Bannockburn battle site. The deoir, hereditary keeper of the relic, and the Abbot of Inchaffray Abbey left the bone behind and brought only the reliquary because they didn't want the relic to fall into English possession. On the eve of the Bannockburn battle, as the deoir, the abbot and Robert knelt in prayer, a noise came from the reliquary. They looked at the reliquary as the door opened and the bone fell to the floor. The Bruce won the battle the next day and he established a monastery to thank St. Fillan for the victory.

No kidding! I have his arm! You can't win!

St. Filian's  Quigrich, or saint's staff, crosier, also known as the Coygerach,is on display at the Museum of Scotland.