This quest is given by Sashra Thaltalis in Zek (+342, -20, -464). It requires that you are level 32+ and have completed the Operation Green Hood quest.
He first sends you to the mine lift to see if it's still functional. Just go there and it'll update your quest. A few orcs will spawn behind you, but you can either sneak through this or fight them--there are about 4, and they don't auto aggro, so if they're greybies, you're all set.
Go back to Sashra, he sends you off to collect five scalps from Sullon Centurians, Tallon Raiders and Vallon Grunts. Grunts are near the lumbermill at 577, -21, -242. Raiders are linked in the camp east of the docks along with Warpriests. Centurians you can find either in a group of two (each a single ^) along the road to the Citadel. You can find a few wandering with a Sullon Lieutenant, and you can find four at the first gate on the way to DFC. This part is timed at 60 minutes, but the timer stops as soon as you get the kills, so it's not a big problem. Once you have the kills, go back to Sashra.
Now that he takes you seriously, he asks you to go kill Sentry Goorlux. Goorlux is spawned by killing a Deathfist Sentry near -108, -23, -282 in Zek. He is a 37 or 38^^ mob. Kill him, then go back to Sashra. Again.
Sashra then sends you into DFC to meet with Infiltrator Stryjin. IMPORTANT - before you enter the courtyard, kill the named in the sewers. If you don't, you won't be able to open the jail door later in the quest. After you kill him, climb the rope up to the couryard.
Infiltrator Stryjin is hiding out in one of the towers around the courtyard, so you'll need to kill the Deathfist townies to spawn the guards and open up the tower doors. Once the doors open up, one will let you use ladders to get all the way up to the ramparts. You'll need to kill all the nameds on the ramparts eventually, so go ahead and get it out of the way. The infiltrator can be found in the SW corner tower where there's no ladder to get up. Just bring a scout with you, much easier that way. Once you meet up with her, she sends you to rescue three trapped Green Hood women inside the citadel.
Two of them are in the jails down below, and one is brewing poisons for the orcs inside. So to get to them, you need to fight to the inner area where Emperor Fyst is, kill all his guards, and make him run down and open up one of the inner tower doors. You fight down through there towards the harem, kill everything in there. Be sure to kill all the named mobs on the harem level. Behind the curtain in the harem room is an elevator, right click on it to activate it. You can go up one floor, kill Warpaw and any nameds there, then go up another floor, kill the boxes and the trained falcon. If the door across the bridge still doesn't open for you, look towards the outer wall and see if you've killed the named mob there. If not, kill him (pullable from there, just jumpcast it) and the door should open. This is the Magus room with the first woman. Kill all the npcs, and hail her with a single click to get credit.
WARNING: When you click on her conversation, she portals out in half a second, so everyone who needs to get credit needs to click at the same time. Have one person call out in /raid HAIL ONCE then CLICK ONCE to time it.
Once you clear the magus room, the elevator in that room goes active, so use it to go down to the midkeep, then go down one flight of stairs. Hang a right into the jail area. One of the women is behind bars, so kill the Jailer to open it up, and do the same process as with the first woman. The last one is just past where the jailer was, another named guarding her, so kill that off, then give her the quest recall stone.
Once you get all three, make your way back to the Infiltrator and let her know what happened. She doesn't depop, so you don't need to fret about timing on this. She lets you know that Fyst was carrying the Short Sword of the Ykesha and you should kill him. So, well, you do.
Go back towards the jail area, then go down another flight of steps before you actually enter the jail. Kill any preaetorian guards there, along with elites. Run through the passages there (not the ones that lead back towards the sewers)--the ones near the henchling bookie. You'll want a scout for this to track if any praetorian guard got stuck in the walls. If so, you'll need to...well, something. We basically trained the entire set of roaming guards along with every named we could find and we happened to get the praetorian in that pull. Once you kill all those, the gates open up into the arena.
The first fight is with four level 40^^^ Deathfist Gladiators. For us, they fought dirty and when we had two gladiators dead, four 40ish ^^^ lions were released on us. Knock all those down, and Dogolka spawns. he was, blue like the others, so could have been 42^^^.
After you kill all that then The Harrower of Zek will spawn. He is a level 40-42 Heroic mob. After he dies Emperor Fyst himself comes down to engage you. I'm pretty sure that he was a 41 or 42 ^^^ mob, so he's raidable, but we did it with 5 people. He has an insane amount of mana, but that's really about it. Kill him.
After killing Emperor Fyst return to Infiltrator Stryjin for your reward.