Morrowind:Morag Tong

The Morag Tong is an ancient guild of assassins headquartered in Morrowind, celebrating murder in the name of Mephala. They have been active since at least the First Era, and their targets have included multiple rulers of Tamriel, high-ranking Dunmer nobility, and countless others. The Morag Tong is unique in its sanctioned status under the Morrowind government to perform legal executions, bound under contracts called 'writs', although extralegal 'gray writs' are rumored to exist.  
Joining the Morag Tong
In order to join the Morag Tong, you'll have to find their headquarters hidden in Vivec, as you cannot join at their local guild halls in Balmora, Ald'ruhn, or Sadrith Mora.

;Headquarters, Vivec: When asking about the Morag Tong, you will be able to find out that their HQ is in Vivec, somewhere in the Arena Canton. If you are lucky enough, you might be able to find someone who knows that it is actually hidden  in the Storage Area under the Arena, just off the western section of the Canalworks. Sure enough, behind some crates, you should be able to find a locked trapdoor which leads to the guild headquarters. Once inside, find  Eno Hlaalu at the back of the top level to begin your initiation. The HQ has several trainers, spell merchants, a trader, and an altar to Mephala.
;Ald'ruhn: The guild hall is located Under-Skar, on the right side in the Manor District. Speak with Goren Andarys.
;Balmora: The guild hall is located in the northwest corner of High Town. Speak with Ethasi Rilvayn upstairs to receive your quests.
;Sadrith Mora: The guild hall is located inside a small mushroom house up a flight of stairs on the northeast side of town. Speak with Dunsalipal Dun-Ahhe.

Unlike other guilds, you can receive regular quests, or Writs, from any of the four quest givers in the Morag Tong, though there are a few specific quests. Similarly, you can report success to any of the four, and not just the one you received the writ from. Advancement in ranks and Special Duties are only given by Grandmaster Eno Hlaalu.

Expulsion
If you make an infraction of the rules, you will be expelled. To rejoin, you must seek a member of at least Master rank and ask about the topic: ''make amends. You will be informed about what is going on: "Your actions of late have not gone unnoticed. There is currently a writ against you. I can have it rescinded, but I must have your word that this was an isolated incident and nothing of the sort will ever happen again. Do I have your word?" Give your word and rejoin, "I will personally revoke the writ. You are reinstated in the Morag Tong as %PCName, the %PCRank. I do not need to remind you the consequences of failing a second time." On the other hand, refusal will result in being attacked, "You were unwise to have contacted me." You will be branded a traitor if you break the rules a second time; speaking to any member of the Morag Tong will result in a salty greeting: "Traitors to the Morag Tong must die."  '' Contrary to what is said, you will not be attacked. You will, however, lose disposition with the person. In the scheme of things, this isn't at all important, as it is impossible to have an accustomed conversation.

Notes
Sometimes when you execute people for the Morag Tong, there will be someone nearby who will report you. Often though, the witnesses will just remain spectators, understanding that you are with the Morag Tong, and don't want any trouble with you, but the rest of the time people will report you to the guards. This has a two-fold effect:
It will halve the disposition increase of the faction members when you go to report on your success
It can get you a bounty

If you are reported, don't panic and restart your game in search of a way around the bounty. If you walk up to a guard and present your writ of execution, he will take the writ and your bounty will be dropped, but you will still suffer the lesser disposition increase with your faction members.  

There is another thing you should be wary of while performing your executions: sometimes nearby NPCs will attack you and support the person you are attempting to execute, making your job harder or endangering important NPCs. Be careful of when you choose to attack the target and in what fashion you attack them. 
To prevent bystanders from joining in, either try to taunt your target first, or use a Frenzy spell, goading them into attacking you. Taunting is rarely an option, because your marks will recognize you as a Morag Tong member and ignore you or beg for mercy, ending the conversation.  (A custom 50-70 pt. Frenzy for 2 seconds, either as a spell or enchanted item works well).
You can use a form of Command Humanoid to get your target to a secluded area.
A third option is to paralyze your opponent before attacking them. Sometimes this will allow you to kill them without other NPCs coming to help so long as the mark doesn't get a chance to attack you.

Morag Tong Ranks

 

Morag Tong Members