Kallas became interested in the history and culture of her new homeland and she joined Noor-Eesti, a sociocultural society which campaigned for the independence of Estonia.

A recurring theme in Kallas's novellas is what she termed "the slaying Eros", a love that often leads to death, especially prominent in her trilogy of Barbara von Tisenhusen (1923), Reigin Pappi (The Pastor of Reigi, 1926), and Sudenmorsian (The Wolf's Bride, 1928).

[3] The Pastor of Reigi and Barbara von Tisenhusen were soon translated into English and published in 1927 as Eros the Slayer.

A collection of her short stories was published in English under the title The White Ship, with a foreword by John Galsworthy in 1924.

Her short story Imant and His Mother was made into opera Mare and Her Son (1935) by Finnish composer Tauno Pylkkänen.