Sky Commander Adaris, it turns out, was not raving after all. The clerics in command have
been shadowy spirits that can't be seen without the elixir. The commander asks you to use
the elixir and slay three of these clerics.
Rilak marvels at the book. It belonged to a talonpriest, beings he thought long gone. The almanac describes how a powerful and terrible Arakkoa king from the past will return. Your only choice, Rilak says, is to summon him prematurely. Rilak urges you speak to Adaris about this.
Upon returning, though, Adaris refuses to believe that attempting a premature summons is the best course. "Your job is done. This is a military matter, now."
A nearby Arakkoa prisoner, Hazzik, overhears these exchanges, and offers to help. He may be imprisoned by the Sha'tari, but under Terokk's reign, he would be a sacrifice. He asks that you pick up a package for him from his hut. Believing Rilak, you have little choice but to trust Hazzik, at least in this.
Hazzik proves true to his word. It seems that Hazzik has been helping the Ethereal smugglers who are looking for rare books. He has a truly pitiful disguise kit, something you'd have to be almost blind to be fooled by. Fortunately, the scribe who has a book with the information you need on bloodlines is almost blind. You don the disguise, travel to the scribe's hut, and buy a copy of the book from him.
To make Terokk's return possible, you have to have an offering to draw him to you. The offering Hazzik makes for you will require a token from each of four of the descendants of Terokk's adversaries.
Much easier said than done. The talonpriests have them captive. But to summon them, you need to capture scrolls from the time-lost Arakkoa. ... for which you need the Elixir of Shadows. And your only way of getting the elixir is by having Severin, the Skyguard medic, make it for you from the Shadow Dust held by the various Arakkoa in Skettis.
So, after a great deal of work, you gather the scrolls, and summon and defeat each of the descendants in turn. On returning to him, Hazzik gives you a bundle of items that symbolize each descenant you defeated, all ready to go for you to summon Terokk.
From the tokens that are taken from each dead descendant, Hazzik also offers to use these items to make another bundle for you, should you need it.
Weak as he is, Adaris gives his blessing to your venture. Bundle in hand, you return once again to the center of Skettis, with the great bone pile upon it. Terokk answers your summons, and with the help of the Skyguard, you manage to defeat him.
Adaris assures you of the lasting gratitude of the Skyguard, and even provides some tangible expression of that gratitude.
In the process of completing these quests you will have gained a great deal more reputation from killing the Arakkoa, turning in shadow dust for more Elixir of Shadows, and collected drops from the various mini-bosses.
Summary
This is part of the the Terokk's Downfall quest chain.