Tribunal:The Black Dart Gang

Quick Walkthrough
#Speak to Narisa Adus in the Bazaar Sewers.
#Speak to Variner's Ghost in the Temple Sewers.
#Either kill the four Black Dart Gang members or flood their hideout.
#Speak to Narisa Adus to receive your reward.

Walkthrough
thumb|Narisa wants justice
A Widow needs your help
In the Sewers of the Great Bazaar, you will encounter the Dark Elf woman, Narisa Adus, located in the western corner, close to the Manor District entrance. She will tell you how she and her lover, Variner, encountered the Black Dart Gang in the sewers. Variner was killed defending her and now his ghost haunts her at night. She asks you to help her by finding Variner's Ghost and pass on any message he might have.

Meet a Ghost
The Temple Sewers can be reached via the Temple's Hall of Ministry, through the Basement, and a trapdoor into the Sewers. Variner's Ghost can be found near the center of this area and indeed has a message for you. It appears that the infamous Black Dart gang can be found in the Temple Sewers West. To make the task easier, Variner will tell you how to kill the gang by flooding the area via a lever that looks like a torch near the east end of the area near the gang. The ghost warns you not to get too close to the gang or you risk the same fate as himself. The entrance to the West Temple Sewers is in the same area northeast or so of Variner.

The Gang's Hideout
The gang's headquarters are in the west section of the sewers, and there are four members to be killed here. The Black Dart Gang member can easily be found within these areas as red-robed Dark Elves. You can kill them if you are stealthy, but their darts do pack quite a punch, so be careful. There is a second entrance which resembles a tunnel, that lends itself to this approach. Alternatively, the torch that Variner's Ghost mentions is just between the doors you entered when going to Temple Sewers West, so it's as far away from the actual gang as you can actually be. The switch will break after you push it, so you can't drain the water that fills the sewer again.

Return to Narisa Adus once you've killed or drowned all of the Black Dart Gang. She will thank you and reward you with Variner's Ring.

Notes
Variner disappears after you speak to him and leave the area.
The best attack here is either a skilled marksman's arrows or ranged paralyzation magicka. The paralyzation allows you to quickly dispatch your foes, while still being able to recover all the deadly darts they would have been throwing at you. Another way to get ready with the gang is to sneak behind (make use of invisibility or chameleon) and ambush them.
If you flood the area, you'll need some form of Water Breathing to collect the available loot; some adamantium armor and of course their deadly darts.
If you flood the area or have a decent levitate/jump spell, you can find an adamantium cuirass in the upper part of the same large room as the box marked "Andren's, Keep Out!".  It is on a ledge near the ceiling.
There is also one gang member in the East Temple Sewers, but he need not be killed for the quest to be completed.
After flooding the area, all torches on the ground will be turned off and renamed "Burned Out Torch". Torches on the walls will instead be labeled "light_com_torch_burnedout_UNI". These torches have a wooden handle unlike normal torches, and are obviously overlooked by the developers, as they have no in-game name and use their Construction Set name. This kind of torch will also disappear if you try to equip it.
If you kill the ghost, Narisa's disposition drops ten points.
(Bugs) if you consider using "the lever to flood the sewers" approach you have to first visit the four gang members to see their corpses, or Narisa Adus keeps repeating "kill them" on mentioning the "black dart gang" topic. She will not identify they are already dead and the quest will not be complete.

Quest Stages