Complex sentence: The Aventine Triad's temple was known by the name of its leading deity--thus, Roman sources describe it as the Temple of Ceres, though within it, each deity had a separate internal sanctuary ("cella").
Split into simpler sentences: The Aventine Triad's temple was known by the name of its leading deity--thus, the Temple of Ceres. Within it, each deity had a separate internal sanctuary ("cella").