Sweyn III of Denmark

Sweyn III Grathe (Danish: Svend III Grathe; c. 1125 – 23 October 1157) was the king of Denmark between 1146 and 1157, in shifting alliances with Canute V and his own cousin Valdemar I. In 1157, the three agreed to a tripartition of Denmark. Sweyn attempted to kill his rivals at the peace banquet, and was subsequently defeated by Valdemar I at the Battle of Grathe Heath and killed.

Source: Wikipedia — https://en.wikipedia.org/wiki/Sweyn_III_of_Denmark