This is a showcase featuring a dialogue-based quest with two NPCs: Othrius and Tolnar. They can be found in Bitter Coast 0, -10 (Tolnar can be seen near Abaesen-Pulu egg mine, and Othrius is a little further northwest). Going up from Seyda Neen, the player will encounter Othrius first. Othrius will claim that a zombie is blocking the road up ahead, and will offer the player 50 gold pieces to kill it.
When the player reaches the zombie (which uses a corprus stalker model), they will find that the zombie can talk. The zombie claims to be a former business associate of Othrius's named Tolnar, and that Othrius killed him out of greed. Tolnar will ask the player to kill Othrius and retrieve a valuable ring from Othrius's body. The player can agree to do so, or kill Tolnar. If the player kills Tolnar, they can return to Othrius for the quest reward of 50 gold.
Alternately, the player can speak to Othrius again. Othrius will deny Tolnar's claim, and offer to pay double for the player to kill Tolnar. The player can refuse, leading to a fight with Othrius. Upon killing Othrius, the player must loot Tolnar's ring from his body, and return to Tolnar (not looting the ring will prompt Tolnar to ask you to retrieve it). Thus avenged, Tolnar will tell the player to keep the ring as a reward and depart from this mortal coil.
If the player accepts the counteroffer, they must go and kill Tolnar. Upon doing so, they can return to Othrius for a reward of 100 gold.
The quest also works if the player speaks to Tolnar before speaking to Othrius.
Outside of the quest .esp, the quest only requires the base game and expansions.