(warning: slight spoilers)
first, become a warrior. after that, click on duskfall.
don't say yes/anything that starts with the letter 'Y' to him.
he'll ask you if he wants to hang out at the shore. do the opposite. say yes.
so head to the shore/where darkclaw will be. keep moving randomly
in the water until he says 'THAT'S IT!' and pulls towards you.
ask him to be your mate, after that.
boom. your mate is now duskfall.