Tribunal:A Star is Born

Quick Walkthrough
#Speak to Meryn Othralas.
#Agree to help him out by replacing Tarvus Beleth.
#Review the script of The Horror of Castle Xyr.
#Speak to Meryn Othralas again.
#Walk to the rug on the stage.
#Deliver your lines.
#Kill the assassin that attacks you.
#Speak to Meryn Othralas once more to receive your reward.

Detailed Walkthrough
Talk to Meryn Othralas in the Great Bazaar to learn that his troupe is performing at the outdoor theatre. Unfortunately, they are without their lead actor, Tarvus Beleth, who has become ill. Meryn explains he is looking to replace Tarvus for their next performance of "The Horror of Castle Xyr" and offers the part of Clavides, Captain of the Imperial Guard. Accept, and he'll give you the  play script. Read the script, focusing especially on Clavides' lines, although you will only need to know the first few pages for the quest. Moreover, while Meryn will ask you to read the script quickly and to speak with him again in two minutes, you are free to take as long as you like reading the script in your inventory. 

After reviewing the script, report back to Meryn and he will take back the book and instruct you to enter through the nearby stage door. Once you reach your stage mark on the rug, the play will commence. The dialogue consists of eight multiple choice 'questions' from the script's first few lines. Any mistakes will result in boos from Jodhur and Nevama Sarobar. The correct lines are as follows:

ANARA: Good evening to you, serjo.

YOU: Good evening. Is your master home?

ANARA: No, serjo, it's only me here. My master Sedura Kena Telvanni Hordalf Xyr is at his winter estate. Is there something I can do for you?

YOU: Possibly. Would you mind if I came in?

ANARA: Not at all, serjo. Please. May I offer you some flin?

YOU: ''No, thank you. What's your name?

ANARA: Anara, serjo.

YOU: Anara, when did your master leave Scath Anud?

ANARA:''' More than a fortnight ago. That's why it's only me in the castle, serjo. All the other servants and slaves who tend to his lordship travel with him. Is there something wrong?

YOU: Do you know an Ashlander named Sul-Kharifa?

ANARA: No, serjo. I know no one by that name.

YOU: ''He's dead. He last said "castle" and "Xyr".

ANARA:''' B'vek, that's strange. I suppose it's possible that my master knew this man, but being an Ashlander and my master being of the House of Telvanni, well, if you'll pardon me for being flippant, serjo, I don't think they would be friends.

YOU: ''Could I look in your master's library?

ANARA:''' Please, serjo, go wherever you want. We have nothing to hide. We're loyal Imperial subjects.

YOU: As, I hear, are all Telvanni.

After delivering the final line--which the script notes is a joke that "never fails, regardless of the politics of the locals"--an assassin named Dravil Indrano will attack you. Once you have killed the assassin, speak with Meryn again to receive his explanation that the lead actor, Tarvus, was not actually ill but rather in hiding from the Morag Tong. Apparently, Tarvus had angered a Telvanni diplomat after pursuing an indecent tryst with his daughter. Meryn will apologise for using you as a decoy and will reward your performance with 2,000 gold (minus 200 gold for each mistake). Only 100 gold is given if you were late to the play in addition to getting every line wrong. By contrast, an Amulet of Verbosity will be awarded if you have made fewer than 3 mistakes.

Notes
Unlike the copies of The Horror of Castle Xyr found on Vvardenfell, this one is not a skill book and will not raise your Destruction skill when read.
The correct line for the first dialogue choice is slightly different from the actual line in the book. Clavides' line in the play reads "Good evening. Is your master at home?" The dialogue choice omits the word "at".
Dravil is equipped with a Daedric wakizashi by a script only after you've said your final line in the play. Thus, while the wakizashi may be considered an additional reward for completing this quest, you cannot steal or loot it from Dravil's inventory at any other time. 

Bugs
 

Quest Stages