Guild Wars 2 – A Sly Trick

It is time to work on the story line some more. Head quickly over to the Grove and make for the Quartermaster's Quarters. Keep on the entry level (the middle level) and head for the Southeastern corner. You will find the entrance to the instance there.

Once inside the instance head over to the right and into the smaller room that Caithe and Tiachren are talking in. Time for a little cutscene:
Tiachren: “The Wardens have had no luck convincing Renvari to tell us what he knows. If he doesn't talk soon, we may never find Ysvelta.”
Caithe: “It's time to try something new. We'll take you into the jail as prisoners and place you in the cell with Renvari. I will give you a key to the cell. Tell Renvari that you stole it from the Wardens, and make your escape.”
Tiachren: “In the cell with him? Caithe, he's a psychopath; that's too dangerous. There must be another way.”
Caithe: “He's one sylvari. There are two of you. The only way to gain Renvari's trust is to convince him that you're kindred spirits.”
Hero: “I'm willing to try. Do you think that pretending to be prisoners is enough to get him to confide in us?”
Caithe: “No. Renvari must also believe you are potential converts to the Nightmare Court. Therefore, during your jailbreak, you will kill me.”
Hero: “What? That's not funny Caithe.”
Caithe: “It isn't meant to be a joke. Don't worry, young dreamer. You play your part, and I'll play mine.”

Follow Caithe back into the Jail past the other prisoners. There are some interesting conversations going on. Once you arrive at the cell with Renvari then head on in. Once the thorns are back in place it is time to talk with Renvari:
Renvari: “This cell's hardly big enough for one, and I've got two idiots clogging it up now? Ugh.”
Hero: “We're not idiots; we just got careless. Next time, that blighted Caithe won't be so lucky.”
Renvari: “She caught you too?”
Hero: “Yeah, but she won't have time to brag about it. A palmed a key from a guard. We're getting out of here.”
Renvari: “Nicely done, I'll admit. But what about the guards? You two won't last a minute against the Wardens.”
Tiachren: “Are you afraid? Look, friend, if you want to stay here, feel free. I thought the Nightmare Court were supposed to be tough.”
Renvari: “You could be trying to convince me to break out just so the Wardens have an excuse to cut me down. It's going to take more than taunts to convince me.”

After all that, it is time to convince Renvari though personality options:
Charm: “Set fire to a few houses. I like to watch them burn.”
Dignity: “Made up reasons to duel, just to kill off weaklings”
Ferocity: “Me? What about you, you sniveling courtier? You should justify yourself to me!”
Normal: “Stole some low-hanging fruit from a sapling”

Choose any of these and Renvari will take to it. After that it is time to break out of the jail and get out of there. Head over to the right of Renvari. You will see a Jail Cell Vine that you can examine. Interact with it to open up the cell. The vine bar now becomes a whip for you. No time to really note its abilities as you are immediately under attack from a Warden. Defeat the 2 Wardens in front of you and then head off to the Northwest.

As you get down to the path expect to be attacked by a Warden and a Fern Hound. Take them out then keep on the move. As you reach the next cell there is another pair of guards to fight though. Take them out and keep going. At the next arch you have another pair of guards to defeat. After that you will encounter Caithe. Her level is not shown but she is holding back for your sake (a newly awaken Sapling stands little change against a former member of Destiny's Edge who defeated a number of Dragon Champions together). With the three of you pounding on her it will take a minute or so, but she will go down. When the fight finishes it is time for another conversation:

Renvari: “You killed her! I'm impressed. The Nightmare Court will welcome you both as heroes.”
Hero: “You presume that we can make it out of here alive. Once the Wardens discover our escape and Caithe's murder, they'll be after us.”
Renvari: “Then we split up and divide their efforts. After we lost them, we can regroup. There's a camp northwest of Aron's Woodlot. Meet me there, and we'll celebrate your victory with our Nightmare brethren.”
Hero: “Looking forward to it. I've wanted to meet the Nightmare Court for a long time. I'll see you soon.”

After Renvari has vanished it is time to revive Caithe. She has only taken a little damage overall and is happy with how the plan has been moving forward:
Hero: “Caithe? Are you all right? Renvari fell for the whole thing, just like you said he would.”
Caithe: “You did well, my friend. I have the bruises to prove it.”
Tiachren: “You were both astonishingly brave. You risked your lives, just to help me save Ysvelta. I'm in your debt.”
Caithe: “The risk was necessary. We needed information, and now we have it.”
Hero: Renvari told us where the Nightmare court is meeting. They'll be keeping the prisoners in their camp. I'm sure Ysvelta will be glad to see us. We'll free her and escape the camp together.”
Caithe: “I hope you're right. We shall see.”

That finishes up this mission, it is time to make on to “Deeply Tangled Roots.” Just head on out of the instance from there.