Complex sentence: In 1887 Pater published "Imaginary Portraits": four psychological studies of fictional characters in historical settings, all of them (in part) disguised self-portraits-a genre in which he came to specialise.
Split into simpler sentences: In 1887 Pater published "Imaginary Portraits", four psychological studies of fictional characters in historical settings, each of them in part a disguised self-portrait. The "Imaginary Portrait" was a genre in which he came to specialise.