How many movies have Erna Morena and Thea von Harbou collaborated on?

They have worked on 4 movies together! Their first movie together was The Indian Tomb, Part I: The Mission of the Yogi (1921) while their highest rated movie together was The Indian Tomb, Part II: The Tiger of Bengal (1921). They have not worked together since Was bin ich ohne Dich (1934). They are most known for their drama films together.