These are the criteria for a secret society:

is exclusive
claims to own special secrets
shows a strong inclination to favor its own

It is exclusive, I don't think they claim to own special secrets, but I am not sure; and they obviously favor their own (hence 'brotherhood').

So can someone confirm whether or not they are a secret society? and on that topic, are there any other secret societies in Tamriel?

All in all, yes, they're a secret society. But 'own special secrets' is largely dependent on what game you're playing. They weren't a 'cult of Sithis' any time before Oblivion, just a clandestine order of super-assassins.

There are a ton of secret societies, depending on how far down you're willing to go. Various Daedric cults being probably the primary amongst them. Thieves Guild is another one (though in Morrowind, they're not exactly 'secret').

I guess they are. I mean you have to kill TWO people to enter the group.

They are sort of like a gang of street thugs, except more gothic and whiny. Also, people are ascared of them.

They do possess secrets, and are privy to certain rare truths - Vicente knows that Janus Hassildor is a Vampire, for example, and implies that he knows you escaped from prison in the tutorial.

I don't think we should take game mechanics too much into lore. I mean, secrecy of the Thieves Guild wasn't the biggest priority of Bethesda, and they were also trying to aim closer to the "casual" gamer. Also, the engine didn't allow for anything like Oblivion, and stealth was pretty bad.

I like to think that the TG is a fairly hard to gain access to secret society. I also think the the DB is, but no so much in game. I mean, if my Orcish barbarian was to kill an innocent bystander, he would be inducted to a group of assassins... Sorry, but no. It's the same thing with Morrowind's, and to a lesser extent, Oblivion's Thieves Guild.

I like how Daggerfall handled it, I would have to be contacted, and I THINK it was based on my skills if I was a stealthy assassin, I'd be inducted into the DB, but I would never get in if I was a warrior. I think we should go by Daggerfall's representation, as they are the same all over Temriel. (unless I'm mistaken)

But, I don't think the Thieves Guild was quite as exclusive as the Dark Brotherhood. Any street pickpocket could join. It's like getting access to an exclusive bar. I actually don't think they were quite that secret. they were secret from the guards and nobles, but I would think pretty much every lowly commoner would know something about them. They seem to just be a group of organised criminals. The only entry requirements would be to seem like a criminal. Imo.


Short Answer:

Yes.

I'd like it if you got into the DB by either a series of murders or the murder of a famous person. The brotherhood then hears about it because they know it wasn't one of theirs, they investigate who did it, then tell you that if you don't join them, they'll turn you in to the cops. That is, if you haven't been caught for it already. They probably don't want someone who gets caught and recognized for that.

What about the Morag Tong?

I guess they sorta count. Then again, the only real qualifications to join them is find their hideouts and the willingness (and skill) to legally slay someone.

They still have their secrets, but being a state-sanctioned guild, they give out plenty of information, and their guildhalls sit in plain sight (as opposed to Camonna Tong and Thieves Guild halls, which always operate behind fronts). Often in the upper-class part of town.

But any secret societies are public, like the Freemasons.

They are more like a business of mercenaries that are state sanctioned so just think of Blackwater of the TES world in a way. Since I haven't played any Morag Tong quests I don't know if they are sneaky or not in their business of eliminating targets.

They don't need to be, they've got legal paperwork. You just kill the person wherever they are and tell the guards that it's all cool.

Oh ok , just curious . Then again it all matters to the member or the Morag Tong and the target selected as well.

Similar to the orcs of Mauloch.

All murder for hire groups are secretive societies. There is a thing known as Imperial Law, which you need to hide from.

The Mages guild does also knows the exact same thing, and is it still such a secret if another faction knows it too?
(Thinking question)

The Morag Tong are as delicate and secret as they need to be. They have a variety of assassination preferences a client can choose which fall under public, private and House war. All pretty self explanatory. If you want a cheeky merchant made an example of, you can have him hit as he crosses Balmora's marketplace to pick up his groceries. Alternately, if your motives were political you could have him done in while he was having a shave at home or stage it as an accident. House war doesn't really require any anecdote at all. As for the recruitment, I'd throw them in as in the same boat as the Thieves Guild. They were made overly simplistic to appeal to casual gamers.

They're public in order for clients to contact them with ease - given that they're a legal and respected entity, unlike the Dark Brotherhood. The Brotherhood are far more mystic, with direct ties (in Oblivion) to Sithis in the form of the strange and supernatural Night Mother, while the Morag Tong is organised like any other guild. I see them as similar to the Assassins Guild of Terry Pratchett's Diskworld, in that they're respected and legally organised, yet aloof and feared (albeit this is in the same vein as respect in this case).

Also, they're not like mercenaries. They're far more precise than that. Blackwater's equivalent in Tamriel would be their parody, in that of Oblivion's Blackwood Company, based in Leyawiin. They're definitely a blunt force tool, as opposed to a finesse based one like the Morag Tong.