I never figured out how to do to get some cards limited as the Blood Owl? I have to buy them? I have to win some tournament? They come out randomly in the packages?
I think it is released on Liquin_3rd's birthday weekend, he is the blood owl. I believe the campaign has been released twice so far. You can not get a blood owl any other way then the campaign, it would make sense to me that the blood owl campaign would be an annual release.
You get it through completing the boon's eve campaign on legendary. I don't think you can currently buy said campaign. It likely will be released again next year on the blood owl's day. So you wait and prey for the favour of the dark and mighty Liquin__3rd etc.