Morrowind:Epony Trade

Quick Walkthrough
# Chat with Nileno Dorvayn about business and ebony trade.
# (Option 1) Travel to Ebonheart and chat with Canctunian Ponius; convince him to buy ebony from House Hlaalu.
# (Option 2) Travel to the Sudanit Mine and kill Darns Tedalen.
# Return to Nileno in Balmora to complete the quest and receive your reward.

Detailed Walkthrough
Ebony Trade for House Hlaalu
Nileno Dorvayn at Balmora's Hlaalu Council Manor will inform you that Canctunian Ponius at the East Empire Company in Ebonheart has threatened to buy ebony from House Redoran unless House Hlaalu lowers its ebony prices. Nileno asks you to either convince Canctunian Ponius to continue to buy ebony from House Hlaalu, or to shut down the Redoran Sudanit Mine by killing the head of mining operations, Darns Tedalen.

Option 1:  Canctunian Ponius
Travel to Ebonheart and locate Canctunian Ponius; he can be found in a back room at the East Empire Company Hall, down near the docks in Ebonheart. Ponius' disposition only needs to be at 75 to convince him, and he'll agree to contract with House Hlaalu for another year.

Option 2:  Shut down Sudanit Mine
Travel to Sudanit Mine, which is located southeast of the Buckmoth Legion Fort. Once there, locate Darns Tedalen, head of mining operations, and dispose of him. This can prove quite a feat; he's in a chamber at the back of the mine, and there are a number of Redoran guards along the way. You will need to provoke him into a fight in order to avoid a bounty since there are plenty of witnesses available to see the murder. One easy way to do that is to climb on to the stone ramp going to the upper ebony deposit where he is standing, you could carefully stick to the walls and reach a point where you can shoot at him via a ranged weapon and avoid detection and avoid alarming the guard, while remaining safe and inaccessible. Doing this requires good timing, and saves at the right points are advisable; attack again only when Darns and his men run to attack you.  Alternatively, use a Frenzy Humanoid spell to make him attack you, leaving you free to kill him without repercussions.  A similar tactic is repeated use of Taunt (which may take dozens of tries if your Personality or Speechcraft are not high).

Consider having Resist Shock effects on standby when fighting Tedalen. He will open up with several casts of a strong AOE shock spell, before switching to a dagger and chasing you. If you're a ranged fighter, just kite him until he runs out of magicka, then hit him at range. The mine is a sloped tunnel, so if you have high enough speed, you can force him to chase you uphill while you get in shots. Just be careful that in the chaos you don't hit any of the other mine's denizens, or you'll have quite the mess on your hands!

Completing the Quest
Return to Nileno in Balmora to complete the quest and receive your reward of 1,000 gold septims. You also get a point of Reputation, ten points of Hlaalu faction reputation and Nileno's disposition rises 20 points. If you perform both tasks, Nileno will also reward you with a pair of glass boots, glass greaves and a glass cuirass, plus you get an extra point of reputation, five more points of Hlaalu reputation, and five extra points of disposition.

This is the last piece of House Hlaalu business that Nileno will have for you; she will now refer you to Crassius Curio in Curio Manor, Hlaalu Canton in Vivec, or Edryno Arethi in the Hlaalu Canton Waistworks in Vivec, for further instructions.

Notes
Despite Ebony being the subject of this quest, the in-game name is in fact "Epony Trade".
This is a very easy quest to resolve, and in true Hlaalu fashion; a little well-placed bribery and/or charm can swiftly secure the Ebony contract for House Hlaalu, making a head-on assault on a Redoran mine completely unnecessary.

Quest Stages