The Jagost is the Zellislava of Drosaico Janovic, one of Rade Sark's chief lieutenants. The Jagost has an unusually shallow beam that allows it to traverse rivers more easily than other ships of its size.
-Jagost is a slavic word meaning "Lobster." This may be a cultural reference to Yog-Tesshecht, who is implied at several points to be the god of lobsters. This would make sense, given that Rade Sark is a Tesshechtite, and Drosaico Janovic is his most fanatical supporter.