Complex sentence: On mosaic floors, the gorgoneion was usually depicted next to the threshold, as if guarding it from hostile intruders; on Attic kilns, the gorgoneion over the kiln door protected from mishaps.
Split into simpler sentences: On mosaic floors, the gorgoneion usually was depicted next to the threshold, as if guarding it from hostile intruders. On Attic kilns, the gorgoneion over the kiln door protected from mishaps.