According to the legend, Byzantine prince with healing powers was called from Constantinople to the northern part of what is today Ethiopia. There, this Abba Garima founded a monastery, and for twenty years performed miracles of healing.
The legend describes some other miracles as well, of a fairly conventional sort. Some of his spittle gave life to a bit of clay. He wrote out the four Gospels in a single day, aided by the fact that God lengthened the day. That sort of stuff.
Here's the cool part, though: the monastery really does own some beautiful illuminated Gospel manuscripts. They are in the Byzantine style, with text in Ge'ez. Scholars have only looked at them a few times over the past 60 years, and the consensus had been that they dated to roughly 1100. Even this would make them remarkably old, particularly since many Ethiopian manuscripts have been destroyed in war.
But it gets better, because a French scholar named Jacques Mercier, presumably with the permission of the monks, removed a few parchment fragments that had broken off, and took them home to be carbon-dated. And guess what? One of the manuscripts may date somewhere between AD 330-540, and the other between AD 430-650.
This makes them among the very oldest illuminated Christian manuscripts in existence. And by the way, Abba Garima is said to have come to Ethiopia in 494, which makes it possible that he really did have a hand in creating these.
Score one for tradition.