I have 3 Marks to defeat in order to complete the game at 100%. Fafnir, Yiazmat and Omega Mark12. The last 2 seem to hinge on Fafnir. I have been in the Silverflows End over 4000 times and that bugger will not show itself. I have tried every trick from past marks and nothing works. I know that he will show in a blizzard. The best I can get is a lite flurry.
When I found Omega Mark12 It was not moving at all, that is why I think that it hinges on Getting Fafnir and then Yiazmat. Please help me.

He only appears on the west side of Silverflows and only during a blizzard. I don't know if the final two hinge on you defeating Fafnir, but it definitely needs to be a blizzard and you just have to keep entering and exiting until the snow is coming down hard.