Or get them from the wine cellar dungeon, really carefully.
Take your best thrall, but arm him the best you can. Let him kill the drunk. The drunk at the start will one shot you. If you are skilled, leave your thrall out of Sepermeru near the entrance that leads to the bar where you find Conan. Go naked with daggers and kill the drunk. With some luck you may loot his truncheon, the best on EL. If you die, you lose nothing and respawn at the entrance for take two. Bleed will kill him. Try to lure him a little away from the door that leads to the other room where there are two relic hunter treasure seekers, usually archers. Once you kill the drunk, go get your thrall. If your thrall is strong enough, just take him with you and let him kill the drunk, as I said. Heal him with cheap bandages or potions if you are in the beginning. Then you will kill the others in the next room. Set the thrall to attack nothing, just in case one is a fighter (your future thrall). I never got a fighter there. Just two archers, that are also very strong, but you may try your luck a little ahead to get a fighter. Now, with your thrall set to attack nothing, send him to kill the first archer. They will both attack your thrall and he WON’T kill the second one unless you order him to. If one of the RHTS is a fighter, you will do the knocking out to capture him. Your thrall will do nothing. Maybe he laughs inside each time you get hit, who knows? If both are archers, let the thrall kill them and help if needed. Healing session afterwards. Then comes the tricky part. You will aggro 3 RHTS when you pass the middle of the ramp you find once you progress any further. Usually one of these guys have fire orbs. Carefullwith them. DON’T fight in the ramp. Lure them up. Otherwise you may aggro a RHTS boss bellow it and they will all come at you. That means death unless you are lvled enough and have a good armor. So lure them. Pick your target. Don’t attack. Evade/ block them while you send your thrall to kill the others. One is an archer and will likely shoot from affar, so don’t worry too much about him, although he may cripple you. Evasion becomes harder, but possible still. Keep an eye on your stamina bar. Once you dispatch those you don’t want or get far enough from the archer, know out your prey. Leave with one of the best thralls in the game.
Now, you can try your luck and instead of picking your target here, you may kill these three and, keeping as much as possible to the left, lure a single fighter bellow without aggroing the boss and his goons. It can be done. If you aggroed the boss, run back, leave the dungeon and go in again. If you didn’t, lure him up. Let your thrall knock him out. Done.
There are easy t4 fighters that you can capture before doing this. Sully, from Sully’s ambush spot is one of these. Level him and you’ll do what I described easily. His spot is above one of the entrances for the Executioner’s dungeon. Search for it online. It’s an easy t4. If you take him to the jungle, it won’t take much until you lvl him to the max just killing grey apes (and gorillas). Level him in the ruins there. These apes are very easy to kill, give a lot of xp and are as dumb as a rock, so you will do fine.
Try to farm a legendary fast. Best bet are stone daggers against a spider world boss. They are very predictable. So, on your way to the jungle, kill one. Take either two pairs of daggers and stone to repair them alternatively, ir take four pairs. That’s what it will take. Make the spider bleed, always keeping at her side and avoiding her special attack. That’s it. The bleeding will kill her. Learn the location if the chest there. Get a legendary every half hour. It will make your life much easier. Then go either for the RHTS or a single berserker that spawns on the mound of the dead. The berserker is harder and if you aren’t high vitality, be very carefull as even with a shield he may obe shot you with the break shield move. Don’t trust your shield when he raises his star metal sword above his head. He will kill you unless you have high vitality. With a lvl 20 Sully, you can easily capture him IF you remember this detail. The second he raises his sword for the downward movement, you immediately roll out. If you are target locked, immediately unlock and gain space. Help your thrall with the shield in all his other moves and you’ll get a berserker early game. Learn his location. So, both situations require skill early game but not too much. Take a Sully first. Sully is easy to capture solo, but if you find it too much, just take a fighter II with you. Any low level thrall, if lvled a bit will do.
So, you have options. Unnamed City, like @stelagel suggested, Wine Cellar or Mounds of the Dead. Once you get one of these thralls, the game becomes much, much easier.