Guild Wars 2

In the crypt where you supposedly find the last book for he mad king tome, Lord Humphrey Faren isn’t appearing no matter how many times you trigger the gaseous search thingy. Anyone know a solution. I really don’t want to miss out on this book seeing as how it’s the last night of the event.

He will run to a corner of the room and hide there. If I am not wrong he is hiding next to the entrance to the room. Not the whole floor is the room only.