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KhittyHawk
Since: Aug, 2009
albinotiger
Since: Mar, 2011
Irrisia
Since: May, 2009

Here's a myth/legend I read a long time ago, but I don't know from which mythology it is and I'm not sure who to ask. Googling the bits I do remember doesn't give me anything. Possibly Greek? Maybe Jewish.
Anyway, (at the tail end of a longer voyage?) this man is told he must slay a monster (residing in a well or some other water source, I think), but that once he kills it he must then kill the first living thing he lays eyes on or else there will be consequences of some kind. He was actually smart and let all the villagers know, but his daughter was so overjoyed at seeing her father again that she rushed out to see him once the monster was dead. I distinctly remember someone other villager calling out "No! Send a dog!" The man can't bring himself to kill his daughter so he kills the dog instead, but bad luck befalls him/his village anyway.
The version I read was in a picture book maybe? It was written more prosaic and and not just summary the way most myths are. Anyone heard anything like this?