Guild Wars 2 –  A Fork in the Road

Head back to the Black Citadel. Use the Hero's Waypoint once again and head to the stockade. It is just to the West of where you appear. Remember that you need to head through the first door on the right. Once inside there you will find the entrance to your next encounter with your sire.

Inside the instance you will find Seneca the Relentless downed. Head over to him and get him back on his feet:
Senecea: “It was the Flame Legion. They came to bust out Forktail right after you left. I-I knew you two were in cahoots.”
Hero: “This is your last warning, jailer: watch how you talk to me. Now, did Forktail resist this breakout, or was he helping them?”
Seneca: “I couldn't tell. They said they were going to kill him if he resisted, and he did … but they just knocked him out and carried him off. Your sire's a snake. I wouldn't put it past him to have staged the whole thing.”
Hero: “Why would he let himself be captured, put me onto their plan, and then break out? No, he was being straight with me, and they came to shut him up.”
Seneca: “We need to find him. He mentioned a Flame bunker in the Arcovian Foothills. They may have taken him there.”
Hero: “Then that's where we'll go. He was your prisoner, so you have a stake in this. Meet me there.”

Leave the first instance and head for the Oldgate Waypoint on the Diessea Plateau. Travel to the Northwest some to find the entrance of the next instance. Once inside you will be joined by your sparring partner. From there just head some to the West to get the ball moving for this part of the storyline.

Secena: “Wasn't sure you'd make it. But I'm glad you're here. Listen to that: they've been chanting since I got here. Makes my skin crawl.”
Hero: “The recruiter mentioned a ritual. We'd better get in there and break it up.”
Secena: “And recover my prisoner. No one's ever escaped my stockades. I know he's your sire, but Forktail belongs in one of my cells.”
Hero: “Tribune Brimstone wants him alive, you want him alive, I want him alive. Let's go get him … alive. Anyone else in there is fair game.”

Head into the ravine in front of you carved into the mountainside to the West. Things are with 2 Stalkers and a Blade storm. After that comes a lot more Stalkers and more Bladestorms. Press on after that fight to reach the higher part of the path. You have a single Flame Legion soldier in your way after taking out all the others. Defeat him and move on.

At the top of the path you have, to start, a Bladestorm, Stalker (both Lvl. 15) and 3 Smoke Shamans (all Lvl. 16). Start this next part carefully as the support part from the Shamans can tip the battle easily. Take them out first to avoid the worst of things. Once they are all done, pound away on the gate holding your sire. Just before you break it down more guards will appear. You can either pause on the gate to kill the guards (and get more experience) or just break it down to press on forward with the story:
Seneca: “Finally back with your Flame Legion friends, eh, Forktail? It's like I always say: once a traitor, always a traitor.”
Clement: “I'm a prisoner here, Seneca. You idiot. They were going to use me as fodder for their ritual.”
Hero: “What ritual? What does it do?”
Clement: “Not here. Get me out of this place, and I'll tell you everything.”

Head back to the Northeast from there, out the riven. When you get down to the first landing a gate will descend behind you. If it comes down in front of you, use a ranged weapon (or a large area attack) to get through it. You have 5 Axe fiends, a stalker and a Lava shaman in the mix. Defeat all of them and finish the descent back out to the plataue. Once there it is time for another talk with your sire:
Hero: “We're clear. Now tell me about this ritual they're planning.”
Clement: “It causes magical fire to burn you from the inside out. It turn flesh-and-blood creatures – like me – into elementals that then fuel a huge burning effigy. The Shaman plans to conduct the ritual inside the citadel, in the Core. He wants to burn all the tribunes and Imperator Smodur. I know where they're preparing the ritual. If you give me a chance to make up for my past mistakes, we can stop this before it starts.”
Seneca: “He can't be trusted. We need to go back to the citadel and warn everyone. We can handle the Flame Legion. This piece of trash belongs behind bars.”
Hero: “Hold on. Give me a minute to think.”

Time to choose which mission you want to take on. Talk with both to learn more about what they can tell you:
Clement: “You barely know me and you owe me nothing – but listen. We can take the fight to the Flame Legion. Let me prove myself by helping to interrupt Shaman Mergath's ritual.”
Hero A) “Why should I trust you?”
Clement: “I won't let my past define me. I followed my warband blindly, gave them my full allegiance. That almost got me killed. I'd rather live out my life as gladium – shamed – then return to the Flame Legion.”
    Hero: “Your warband?”
    Clement: “yes. When they joined the Flame Legion, I thought I had to join too. I was mistaken. They had betrayed our legion and me. I learn then that loyalty to the legions outranks loyalty to your warband.”
Hero B) All right, Forktail. I'm willing to trust you.”

Seneca: “You can't trust him. Come on, let's go back to the citadel and warn the tribunes.”
Hero A) “Why shouldn't I trust him?”
Seneca: “He's a Flame Legion Shaman. He could have turned his warband in when they first started sniffing around the Flame. Did he? No. What kind of soldier does that make it?”
Hero B) “Agreed. I won't risk the Citadel on his word.”

Siding with Seneca leads to the mission, “Tribunes in Effigy” while siding with Clement starts the mission, “Sins of the Father.” The choice is yours.