Obtain an oilcan from Sarin, in A Stone Dwelling of a Maradas Follower (73487), you can get a visible evil second class to get one and mail it to you (go in and out of the room until he asks a question and sayto him yes twice). Obtain matchbook from the merchant (Mikka) that walks around town.
Go to Nelinde, in The Dwelling of an Ithrilis Follower (73432); hold the can; use the oilcan 4 times to empty the contents; remove and drop the can; open matchbook; get match matchbook; hold and drop match; then, get out of the room. The room will engulf in flames. You will hear Nerinde dying. Do not re-enter the room, you will instantly die. If you have trouble understanding this and choose to die in the room you can go back and get the mark after you res.
Return to Sarin and obtain mark. You may have to go in and out of the room to get it to work. You still need to be visible for him to give you the mark.
For lighting the fires while the city sleeps, the Powers have granted thee a Mark. You have been granted The Mark of Revenge! You gain 45 practices!