Schlossar was born in Troppau in Austrian Silesia (now Opava in the Czech Republic), son of a tax official.
The family moved to Kronstadt (now Brașov in Romania) where he was educated, and in 1867 to Graz, where he studied law, receiving his degree in 1873.
[1][2][3] He did not like working in court, and in 1875 he became an amanuensis, or secretary, at the University of Graz Library.
Works include Erzherzog Johann von Oesterreich und sein Einfluß auf das Culturleben der Steiermark ("Archduke John and his influence of the cultural life of Styria") (1878), for which he received the Goldene Medaille für Kunst und Wissenschaft, and Oesterreichische Cultur- und Literaturbilder mit besonderer Berücksichtigung der Steiermark.
He contributed to magazines such as Das literarische Echo in Stuttgart and Bühne und Welt in Berlin.