Here's an actual Midnight leak.
>Expansion is mostly existing to remind the Elves that they owe a debt to the Lothar family
>Xal'atath corrupts the sunwell to channel a portal to gain access/control of Azeroth's world soul, thanks to the Sunwell being made from water of the Well of Eternity.
>Faerin uses her family abilities gifted to her by the Scions of light to purify the Sunwell and by extension Azeroth of void corruption
>But this puts her in connection with Azeroth's spirit itself and thus she evokes the debt to the line of Arathi and orders the Elves aid her in freeing Azeroth from the chains the Titans bound her in
>The quest starts in Northrend and this is the initial set up to Last Tit.