Sunken City isn't easy. It's going to be hard for a level 20 to finish it alone. You'll need a team, preferably with a few higher-level wizards. Fortunately, it isn't needed to advance or receive spells until level 38, by which time you should be able to do it.
i got the qwest at level 5.level 20.....yet to finsh.
how did you get the quest at lvl 5?! I got it when I was a lvl 16.... and I would gladly help you complete the quest because I'm stuck as well. This is no offence to you, but what school are you? I'm a life(at least, the only one out of my 6 wizards that can go to sunken city) and you will need a healer( no offence again.)
I'm a level 34 life wizard and I got the quest at level 12, I tried to solo it at level 14, but couldn't, so I went to colossus boulevard and started Krokotopia for a few levels until I got to level 18 then did my spell quest, and I solo'd sunken city with ease with my forest sprite. Anyways, how to do the dungeon? First you find Marla Stinger, then she tells you to go to a tower, which will have 3 wailing wraiths in it that are death with 575 hp each. I recommend that you try to get a minion out as soon as you can. Soon enough, they'll start attacking your minion so it is sort of a shield. After you finish the battle, you talk to Marla again, then you fight Paulson in a tower with 2 wailing wraiths. Paulson is death and has 800 hp. After that fight, use the knock scroll it gives you to open the gate, and then you go into Nelson's building. There are a lot of fights, but I can't remember which order. I just remember that there are wailing wraiths, myth monsters, and Norton. After you finish Nortons tower, you're up against Grubb. He is 1000 hp death with a minion of fire. Good luck! Hope I helped!
Sunken City is a lot easier than what it used to be. Mobs used to pull you off the sidewalk, and it was incredibly hard for lower levels. How to get the quest: go to Nightside and pick up the quest from Marla Stinger. Go through the small story, and then ask some friends to go with you. It's important to ask friends for this dungeon because it can be hard for someone who doesn't know how to play that well. Make sure you stock up on potions, because these are nice after a battle and you need health/mana and there are no health wisps around. Lastly, make sure you have enough time to do the dungeon. If you're all defeated, or if you're all gone, the dungeon will reset in 15mins. After you're defeated, you can always use a potion and run back in before it resets! Hope I helped you somewhat.