The Daemonheim aura 4 is a reward from completing the Elite Daemonheim achievements given to you by Thok. It can be retrieved from him for free if lost.
You can activate and wear the aura outside Daemonheim, and it will last for 1 hour. After being activated, it will need to cooldown for 4 hours.
Whenever the player enters a floor in Daemonheim, the aura will automatically be equipped.