Principality of Chernigov
Mstislav III Glebovich (before 1215/1220 – after October 18, 1239) was a Rus' prince (a member of the Rurik dynasty). He was probably prince of Rylsk (1212–1239/1241) and of Chernigov (1235–1239/1241). During his reign, the Tatars (the Mongols) invaded and pillaged the towns of the Principality of Chernigov.