Online:The Anger of a King

Quick Walkthrough
#Talk to King Kurog.
#Find Eveli Sharp-Arrow.
#Convince Eveli not to give up.
#Meet the scouts outside Paragon's Remembrance.
#Infiltrate the Vosh Rakh and discover their plan.
#Warn Eveli about the Vosh Rakh's plan.

Detailed Walkthrough
You will be offered this quest when next in Orsinium after completing To Save a Chief, by Shield-Wife Razbela running up to you and calling for your attention.

When you leave the keep, a messenger is standing there with a letter for you from Eveli. You have the option of talking to Owayine, the messenger. If you talk to him, he suggests Kalina at the Mages Guild may help decipher the message. She is unable to provide much help, but if you bribe her she suggests checking at the Outlaw's Den below the city. There, approach Watzhi Fast-Claw. If you pay her, she also will not tell you what the message says, but will hint that you should look at the first word of each sentence.

The message says: We are at the inn. Hidden Room. Secret words: Orcs don't smell. The inn referenced is the Greedy Gut. Head up the stairs and talk to Mulzah.

In Paragon's Remembrance, after most quest objectives you will have the ability to talk to Talviah for more details or his thoughts. He has a quest marker but no objective appears in the journal or the tracker. When you get to the Chambers of Loyalty, you will be given the choice of three "blessings" to help you during the trials. One will increase your run speed, one will increase your defense, and one will increase your attack. The timer is set for two minutes and 30 seconds, so you must be quick.

Recommendations: Carefully study the map before you enter. Run through enemies to confront them in groups to save time.

When you reach the next room, the Vosh Rakh will have seen through your disguise, but you will be given a choice: sacrifice Talviah to prove your loyalty / conversion to the Vosh Rakh, or else take on everybody else in the room.  

If you kill Talviah, you will see a vision of Forge-Mother Alga, welcoming you into the Vosh Rakh fold, and explaining that the Vosh Rakh were the true attackers at the Temple, dressed in the robes of Malacath and shouting the names of Malacath and Chief Bazrag: and that they intend to attack and murder the remaining chiefs at Kurog's Moot, recapture and kill Bazrag as he escapes, and pin the entire blame on High Priestess Solgra - a Trinimac cultist who is not a member of the Vosh Rakh, who has just helped you rescue Bazrag.  

If you choose instead to take on the whole roomful of cultists, Talviah will survive but it is a tough fight against a dozen enemies, and you can learn an incomplete version of their plans by reading the "Vosh Rakh Orders" document: and you do not see the vision of Alga, or learn of her involvement, and you do not learn that Solgra is also in danger.

When you come out, you'll meet Eveli in the chamber outside. If Talviah is not with you, she'll ask questions, and you can either tell her the truth (you sacrificed him to gain knowledge of the Vosh Rakh's plans) or lie and say that he sacrificed himself for the cause. If you tell her the truth, she will accuse you of being as great a monster as the enemies you and she are supposedly fighting, and resolve to leave Orsinium after its political crisis is over - even though she will accept your word, that Bazrag and Solgra are both in immediate danger. If Talviah is with you, you've still learned something about a planned Vosh Rakh attack on the moot, and that there are Vosh Rakh among Kurog's soldiers.  

Either way, make your own way out of the fortress.  The front entrance is nearby: alternatively, if you have started the sidequest Forcing the Faith, now would be a good time to finish it and give the Vosh Rakh plenty more to remember you by.

Notes
You do not have to go through and decode the letter. You can decode it yourself, and head straight for the inn.
If you can't defeat the Vosh Rakh council, you will be forced to sacrifice Talviah to progress the quest.
If you have Lightning Form active at the start of the sequence where you have to chose to sacrifice Talviah or not, he may be damaged and become hostile precluding any choice.
If you do not sacrifice Talviah, High Priestess Solgra will die later in the questline.
 

Quest Stages