King Cyzicus in Jason and the Golden Fleece
A highly unfortunate king who is at first very friendly to the Argonauts. When the band of heroes accidentally returns to his island at night, however, Cyzicus mistakes them for enemies, attacks, and dies in the battle. His wife is so upset by all this that she kills herself. Jason feels more than a little crummy that the friendly king had to go out like that, so he makes a bunch of sacrifices to the gods and holds some funeral games. Cyzicus was the name of an actual city that existed in what is today northwestern Turkey. It was said to have been founded by Thessalians, Greeks from the region as Jason, and so you get why the king might initially be friendly to the Argonauts.