If you’ve been following things and watched the video, you no doubt have some basic knowledge of Algalon the Observer and that he’s only tuned as Hard Mode. This fellow is essentially the conduit between the Titans (who have left Azeroth) and the Watchers (Freya, Mimiron, Hodir, etc.). It turns out — thanks to some data on Wowhead from the 3.1 PTR — that Algalon is preparing to alert the Titans of what’s happening in Ulduar, and there’s an urgency to stop this. If the Titans discover how dire the situation is, they may decide the only course of action is to wipe the slate clean by “sterilizing” the planet.
This information also makes it clear that you’ll only be able to access Algalon after redeeming the Watchers; there are a set of quests involved in it and turning in each of the sigils of the Watchers will grant you access to the Celestial Planetarium — Algalon’s chamber.
The first quest in the chain looks to be Archivum Data Disc (Heroic: Archivum Data Disc). Where this comes from is still to be determined. Since Algalon himself is only available in a Hard Mode version, it can be assumed these quests may only be completable from the Hard Modes of encounters in Ulduar.
Brann Bronzebeard has discovered that Algalon the Observer is going to be arriving in Ulduar soon and will likely send back information on what’s going on.
Listen, <lad/lass>! Azeroth’s fate is at stake here.
Our only chance is to get to the Celestial Planetarium in time to find this Algalon and stop him from beaming back any messages to his Titan masters.
Locate the Celestial Planetarium and come back with any information you get. We might still have some time to prepare for Algalon’s arrival.
Sigils of the Watchers
Next up you must obtain the Sigils of the Watchers so that you can use them to access the Celestial Planetarium and stop Algalon.
This looks to be the quest that will unlock the Celestial Planetarium, allowing access to the Algalon the Observer encounter.
You really did it, <name>. Take the sigils to the Archivum Console and see if you can gain access to the Celestial Planetarium.
You best hurry, <lad/lass>. Time is of the essence.
This is likely one of the last quests in the chain; you’re to take a code to Rhonin in Dalaran so it can be altered to let the Titans know that everything is peachy on Azeroth.
We’d best hurry now, <name>. We’re going to have to transmit the reply-code from the Dalaran.
Take it to Rhonin, I will meet you there.