Words cannot express the debt I owe you for helping return my daughter to me, but unfortunately the traitor Ashvane has left us no time for celebration.
We must act.
Notes
Map of the "Thros, the Blighted Lands" scenario.
Take the Portal to the Blighted Lands to enter the "Thros, the Blighted Lands" scenario:
Stage 1: The Blighted Lands
Follow Katherine into Thros, the Blighted Lands.
Follow Katherine
A vision of Jaina as a child appears:
Jaina says: It's... all my fault...
Katherine Proudmoore says: Jaina?!
Jaina says: No! Stay away!
Katherine Proudmoore says: Jaina, wait!
Stage 2: Chasing Shadows
Jaina has fled deeper into the Blighted Lands. Follow her.
Katherine Proudmoore says: My daughter is here somewhere. Hiding. Suffering.
Katherine Proudmoore says: We will find her... and free her from this forsaken place.
Head west to find Jaina staring at Daelin Proudmoore:
Daelin Proudmoore says: You stood and watched as those animals cut me down. What has your betrayal earned you?
Jaina says: Father... please...
Daelin Proudmoore says: They took your father... betrayed your king... and you did nothing! Will you abandon all your allies to the Horde?
Katherine Proudmoore says: Enough! Show us your true form, monster!
Daelin Proudmoore yells: Insolent fools! She is broken beyond your reach!
Defeat it:
Daelin Proudmoore yells: You will be next!
Blighted Deciever says: You are... too late...
Katherine Proudmoore says: Jaina? Is it really you?
Interact with her and a cinematic plays, the Realm of Torment:
Katherine Proudmoore: There you are...
Jaina as a child is turned away, sitting on a ruined part of a building, head in her hands and crying.
Young Jaina: I did everything wrong.
Katherine gently reaches out to touch Jaina, but just before her hand does so, the girl's body disperses like smoke. Shocked, Katherine looks around as the scenery surrounding her disappears into black and her body is rocked by the entry into Jaina's Realm of Torment. She hears a man's voice.
Arthas Menethil: We're too late.
A brief portion of "O Thanagor" plays as Katherine turns to her left and sees Arthas standing on a small rise, staring off into the distance before looking back.
Katherine follows Arthas's gaze to her right and sees Jaina, looking as she does today, but re-enacting her actions from her memories.
Jaina Proudmoore: I'm sorry Arthas. I can't watch you do this.
Jaina turns and leaves, her thoughts echoing.
Jaina Proudmoore: (thinking) We should have stopped him. He never would have turned. He'd still be alive.
As Katherine tries reaching out towards Jaina and falls short, a familiar voice is heard.
Daelin Proudmore: You have always been naive, my daughter.
Katherine Proudmoore: Daelin?
Katherine turns in the direction of her husband's voice and sees the distressed Jaina and the hardened Daelin having an argument by a fountain, from Daelin's first arrival on Theramore Isle.
Jaina Proudmoore: I won't let you do it, father!
Jaina Proudmoore: (thinking) I should have tried harder.
Jaina Proudmoore: You don't understand!
Daelin Proudmoore: I understand more than you suspect, my dear.
Jaina Proudmoore: (thinking) I wasn't strong enough.
Jaina Proudmoore: (thinking) I should have made him listen.
Jaina Proudmoore: Father, no!
Jaina Proudmoore: (thinking) Forgive me.
The truth sadly dawns on Katherine's face as she realizes the circumstances of Daelin's death.
Katherine Proudmoore: You couldn't save him... from himself.
Daelin Proudmoore: Do you really think you can cast aside your guilt so easily?
Daelin's voice roaring around her, Katherine grimaces and clutches her head, gritting her teeth at Jaina's scream. As the scream fades and is replaced with a heart beating slowly, Katherine sees Jaina from behind on her knees, cradling Daelin's dying body in her lap as she cries. His heartbeat slows to a stop.
Jaina Proudmoore: No. Father... why wouldn't you listen.
Placing her hand over Daelin's chest, Jaina's thumb and forefinger brush the Proudmoore pendant still hanging around his neck.
Priscilla Ashvane: Katherine...
Katherine turns her attention left to Jaina's arrival in Kul Tiras.
Priscilla Ashvane: Enforce our laws. The punishment for treason... is death.
Memory Katherine walks forward revealing Katherine in the background, watching the scene with regret.
Katherine Proudmoore: Do you accept the judgment of your homeland?
Jaina Proudmoore: I accept your judgment... mother.
Determined, Katherine steps forward and swipes away her memory self to smoke, then reaches out and lifts Jaina's chin. She jerks a little at the contact, her eyes fluttering as if half-awake.
Katherine Proudmoore: My daughter. Forgive me.
Blinking, Jaina opens her eyes at Katherine's voice full of love and looks up, surprised to see her mother in front of her.
Katherine Proudmoore: Forgive your father.
Jaina turns to look as the men and women behind her fade away, with the exception of Daelin, but for a moment.
Katherine Proudmoore: And... forgive yourself.
Katherine reaches back out and caressing her face, turns Jaina back to face her. The color returning to her, Jaina leans her cheek into Katherine's hand as the scene fades to white. A younger Katherine can be heard calling Jaina back in her youth.
Katherine Proudmoore: Come topside, sweetheart.
Awakened from her memories, the real Jaina sits where her child self was, back in Thros, Katherine's hand on her pauldron. Raising her head and opening her eyes, she turns to the weight on her shoulder to see her mother, who caresses her face once more before they lean into each other and tightly embrace.
Final Stage: Facing Fate
Defeat Gorak Tul and escape from the Blighted Lands.
Escape the Blighted Lands
Katherine Proudmoore says: Come, daughter. We'll find our way out of here.
Behind Katherine just outside the circle of stones, Gorak Tul appears!
Gorak Tul yells: None of you will escape!
Lady Jaina Proudmoore says: Mother, look out!
Tul blasts Katherine, knocking her to the ground.
Lady Jaina Proudmoore says: Mother!
Jaina teleports in between Katherine and Tul and AOE blasts him back. She snarls her response.
Lady Jaina Proudmoore says: You challenged the wrong family, fiend!
Tul attacks
Lady Jaina Proudmoore says: To arms, <name>!
Gorak Tul yells: Thros will consume you all! At last I will claim vengeance!
Defeat Gorak Tul:
Lady Jaina Proudmoore says: My people defeated your kind once, monster. We will do so again!
Tul collapses.
Gorak Tul says: Your hollow victory... means nothing...
Gorak Tul says: The Drust... will never... relent...
Dying with his last breath, Tul's corpse fades away. Jaina responds firmly.
Lady Jaina Proudmoore says: And Kul Tiras will never yield.
Jaina teleports back to Katherine, who is kneeling.
Lady Jaina Proudmoore says: Mother! Are you alright?
They stand up together. Katherine just sounds a bit winded.
Katherine Proudmoore says: Yes... I will be fine.
Katherine Proudmoore says: We'd better go before more of those... things... arrive.
Lady Jaina Proudmoore says: It will be a relief to put this place behind me.
She turns to you.
Lady Jaina Proudmoore says: <Name>, shall we?
Speak with Jaina:
I can teleport us out of here when you are ready, <class>.
Please hurry, I wish to be rid of this place.
I'm ready to leave.
Lady Jaina Proudmoore says: Very well. Come, mother. Time to go home.
Jaina teleports herself, her mother, and the adventurer out of Thros.
Finale
In front of Proudmoore Keep where they last saw each other, the two Proudmoores stop for a moment to gather themselves.
Lady Jaina Proudmoore says: It is good to feel the sea air. Thank you, <name>. Without your intervention, I may never have felt it again...
Katherine Proudmoore says: Now, let me see if I can do this properly this time... Welcome home, daughter.
Thros, the Blighted Lands
[Radiant Azerite Core] (750x 
[Azerite])
80
[50] Runic Resistance
I'm ready to leave.
[The Pride of Kul Tiras]" achievement, but the storyline continues with 
Patch 8.0.1 (2018-07-17): Added.