Blizzard has released a new in-game cinematic titled “Opening the Way” which shows how the entrance to the Zaralek Caverns were formed.
Towards the end of the cinematic we hear the following:
Vyranoth: Exquisite. In his wake, the Dracthyr will succumb to the temptation of Aberrus and unleash the Aspects’ darkest nightmares.
Iridikron: Come. We have much do do. Let the children of Neltharion claim their birthright.