Taken from UESP:
Speak with Marena Gilnith in the Great Bazaar area who wishes to meet someone new. Agree to hear her story and she'll go on to tell the story of how she ran away to Mournhold in hopes of meeting and marrying a man of her dreams. Unfortunately, she has been unable to make very much money and has had to resort to working all the time to survive, never having a chance to meet any nice, single men. She asks you to keep an eye out of anyone that might be interested in meeting her.

On the other side of the Great Bazaar you'll meet Fons Beren who claims to get on quite well with the women, as he humbly puts it. Suggest that he meet up with Marena and return to speak with her. She seems hesitant to meet him but eventually agrees to meet up with him. Return to Fons to setup the meeting and that's that (I couldn't find any way to continue on with this). Return to Fons sometime later and he'll refuse to speak with you as he is preparing for his date.

There is another man that will be willing to meet with Marena, Goval Ralen in the Temple District. Just speak to him about woman and he'll be ready to go. If you've already setup her and Fons, however, that's all you can do. Personally I wish I had setup her with Goval. If you do set her up with Goval they will eventually get married. After the wedding (some days afterwards you can see them outside the tavern) they will give you a present (a +15 luck amulet).

You can also pair her up with Sunel Hlas, a trader who is mourning and bitter about the loss of his wife in the Great Bazaar. Mention women and marena to him and he'll agree to a date reluctantly. When you speak to Sunel after setting him up he'll tell you to leave him alone, but you should get three options to reply with. Choose the 'optomism' response and end the conversation. The two will arrange to meet at the Winged Guard and after some time both parties will return to the Bazaar. Depending on the advice you gave (or didn't give) Sunel, the date may end up horribly or very well. If you gave the 'optimism' advice you'll find Marena upstairs in his shop (guess it went well). Sunel will reward you with the Bipolar Blade.

Bipolar Blade
Chop: 5-61
Slash:1-50
Trust:1-35
Condition: 4300/4300
weight: 42.0
Value: 40000
Cast when Strikes
Frenzy Humanoid 30 points for 15 seconds
Calm Humanhoid 30 points for 15 seconds