Does every player in the raid group need to be attuned or just the ones that open the door?
Er’body.
You will soon be well acquainted with the people’s champion himself: Rexxar.
Every player needs to be attuned. Attunement is a per character thing. Once you are attuned you still need to have the Drakefire Amulet in your bags otherwise you cant get inside the lair. It’s the key.
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The Onyxia door is tricky, it opens only for your client. If you are standing there and someone who isn’t you opens it, you don’t see it.
I did find out last night that you don’t need to be wearing it to open the door.
Yes. You need to have the necklace in your bag in order to enter the Lair.