The Duchy of Holstein was established by a Scandinavian monarch under what union?
Christian I of Denmark Christian I (February 1426 – 21 May 1481) was a Scandinavian monarch under the Kalmar Union. He was King of Denmark (1448–1481), Norway (1450–1481) and Sweden (1457–1464). From 1460 to 1481, he was also Duke of Schleswig (within Denmark) and Count (after 1474, Duke) of Holstein (within the Holy Roman Empire). He was the first Danish monarch of the House of Oldenburg.
Eric XIV of Sweden Eric XIV (Swedish: "Erik XIV" ; 13 December 1533 – 26 February 1577) was King of Sweden from 1560 until he was deposed in 1568. Eric XIV was the eldest son of Gustav I (1496–1560) and Catherine of Saxe-Lauenburg (1513–35). He was also ruler of Estonia, after its conquest by Sweden in 1561.