I was also stuck here with my lvl 70 char (Dragonflight) until just now. You have to pull the boss with your body, then wait until the first add spawns, kill it and then kill the boss. The kill will then count towards the quest.
Quest
Closing a Dark Chapter
A World of Warcraft quest in Grim Batol. Facts and objectives from the current retail game data.
At a glance
Closing a Dark Chapter is a dungeon quest for level 30-35 in Grim Batol. It rewards 3 reward items, 4,800 experience and money.
Quest facts
The client quest POI data records no map location for this quest, so no map is shown.
Check whether you have already completed this quest
in-game: /run print(C_QuestLog.IsQuestFlaggedCompleted(28854))
Description
This terrible place was Alexstrasza's nightmare. During what mortals call the second war, she was chained in the depths below, her tormented offspring forced to serve the demon-corrupted Horde. Alexstrasza may be free, but the beast known as Erudax still corrupts her offspring below. <Baleflame's body tenses in anger.> Destroy him, {class}. Crush him that we may end these horrors once and for all!
Getting there
Inside the dungeon: Grim Batol
Don't be fooled by Grim Batol's humble exterior; many of this mountain fortress's desecrated chambers are buried deep in the Twilight Highlands. Once the stronghold of the Wildhammer dwarves, and later seized by orcs as a prison for Alextrasza, the city is now in the clutches of the Twilight's Hammer cult.
Bosses in the Adventure Guide, in order: General Umbriss, Forgemaster Throngus, Drahga Shadowburner, Erudax, the Duke of Below.
Entrance: Grim Batol, Twilight Highlands at 19.1, 53.7.
Instance text, bosses and entrances are the client’s Adventure Guide data.
Community notes from Wowhead · 2 comments
The comments below were written by Wowhead users. They are community notes, not TheWoWDB comments. See them in context on Wowhead.
Anyone else have trouble getting the rewards off this quest?
I've had problems with 2 different characters who did this and I had to log out and back in several times before it worked.
Choose one of these rewards:
Reward details
Pick one of these
Item facts are the current retail client’s (ItemSparse); the specialisations for a pick-one item are the ones the Blizzard quest API lists; faction and currency text is the client’s own. Lowest listed price = the US commodity auction house now.