Just checked in my questlog, I've got the achievement, for sure it was few years ago but for sure I never paid a visit to Vengoth Castle. Maybe after saying "alori mort" to Armenius, he teleported me to some cage with him. I'll try to do the quest on other char and watch my Server Log then. Van Rebeliant (talk) 06:02, January 15, 2013 (UTC)
Getting this achievement randomly is one way. But every player has a chance to get this schievement another way, if he didn't get it during Blood Brother quest. I heard that if you wait long enoughh invisible in Armenius tavern, he will change into vampire for a brief moment, and you can earn this achievement this way. But i have never had patience to test it myself.
Mathias mentioned in his edit on this achievement page that after completing the quest, you have 1 chance each day to get teleported to face armenius, does anyone know where this info comes from? Is this actually true?