TheWoWDBTo put it bluntly, this is a quest to do a raid.
Quest
Heart of the Sepulcher
A World of Warcraft quest in Sepulcher of the First Ones. Facts and objectives from the current retail game data.
The highest voted Wowhead comments for this page. They are community notes, not TheWoWDB comments.
To complete this quest on LFR you must queue for "The Grand Design" where The Jailer is the only encounter for the queue.
The prerequisite for this quest appears to be completing chapter 4 of the campaign.
Quest facts
Quest ID65259
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(65259))
Description
Soon after we stepped forth into the realms of Death, a message left behind by the Primus gave warning that the Jailer must not be allowed to reach the Sepulcher. Despite all our efforts, he has done so. Within the heart of that ancient place lie secrets the Jailer could use to dominate the entire cosmos. If he succeeds, everything we hold dear will be lost. Gather your allies, {name}. Claim victory for the Shadowlands... and for Azeroth.
Getting there
Inside the raid: Sepulcher of the First Ones
The Jailer has breached the Sepulcher, the mysterious heart of the Shadowlands. Should he control its primordial power, he will reshape the cosmos with Death at the fore. As Zovaal prepares to dominate reality, champions of Azeroth charge forth to stop him. Will their resolve outmatch his?
Bosses in the Adventure Guide, in order: Vigilant Guardian, Skolex, the Insatiable Ravener, Artificer Xy'mox, Dausegne, the Fallen Oracle, Prototype Pantheon, Lihuvim, Principal Architect, Halondrus the Reclaimer, Anduin Wrynn, Lords of Dread, Rygelon, The Jailer.
Entrance: Zereth Mortis at 81.0, 53.3.
Instance text, bosses and entrances are the client’s Adventure Guide data.
Community notes from Wowhead · 7 comments
Top 3 shown aboveThe comments below were written by Wowhead users. They are community notes, not TheWoWDB comments. See them in context on Wowhead.
The top 3 are shown in Top Comments above. Read all 7 on Wowhead.
Reward details
Reputation: The Enlightened +1,000
Once members of Cartel Al, the Enlightened have abandoned the pursuit of profit and glory out of devotion to the First Ones. By earning their favor, the brokers may be willing to share the knowledge they have gleaned.
Reputation group: Shadowlands.
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.