Pierre-Hubert Subleyras
St. Basil Celebrating Mass Before the Emperor Valens

1745
Oil on canvas
Church of Santa Maria degli Angeli e Martiri

According to one source on the internet, the painting is based on a legend in which St. Basil's devotion in celebrating this mass was so great that it caused the emperor to faint and then to convert from Arianism to Catholic Christianity.  The emperor does seem to be fainting in the image, but I have not yet found any other literary or pictorial instances of the story.  In fact, Valens never did convert.

More of St. Basil

Photographed at the site by Richard Stracke