Wikipedia
According to the Golden Legend, Ephigenia was the daughter of Ethiopian King Egippus. She was dedicated to God by Saint Matthew. When Hirtacus succeeded the King, he promised the apostle half of his kingdom if he could persuade Ephigenia to marry him. Matthew thus invited the king to Mass the following Sunday where he explained that she was already espoused to the eternal King and thus could not be purloined by Hirtacus. The king thus sent a swordsman to kill Matthew who stood at the altar, making him a martyr.
Not having managed to bend Ephigenia to his will, Hirtacus tried to destroy her home with fire. However, the apostle appeared and warded the flames from the house, turning them upon the royal palace. The king's son was seized by the devil and the king himself contracted leprosy, eventually killing himself.
The people thus chose Ephigenia's brother as their king, who reigned for seventy years, leaving his kingdom to his son who filled Egypt with Christian churches.