Calmasis was the main character of alpha Rose’s book series, Complacency of the Learned. Alpha Rose had visions of Calliope and Caliborn’s life and wrote a book about it as a warning to the Condesce that she knew who her employer was.
Popular head canon because of the strong parallels between the slave and Kanaya. The romantic situation between Vriska and Kanaya then Mindfang and the slave. Dualscar killing the slave and Eridan killing Kanaya. Also on this page it says the Dolorosa was sold to seadwellers as a slave after the Signless was killed and Dualscar is a seadweller.