The Nyköping Banquet A gruesome key story from the Middle Ages Eric’s Chronicle, written in the 1330s, is one of a series of medieval chronicles of the kings of Sweden. A large part of it is about the Nyköping Banquet, a grisly drama in which a key played a crucial role. A tale of power struggle, schism, injustice, revenge and cruel death that unfolded in the Nyköping Fortress. The key that King Birger threw into the Nyköpingsån River had just locked in his two brothers, Dukes Eric and Valdemar, in the fortress dungeon to die in torment and starvation. What did the key sinking into the riverbed look like?