Dark Brotherhood

HAIL SITHIS! sorry, needed to get that out of my system.

definately need the brotherhood to be a force to reckon wiith. None of the we are on our last legs stuff like oblivion and skyrim portrayed. And more than one sanctuary.
also they could have one of the fighting temples as a training ground. But not obvious to outsiders.

Well, of course, I would never allow for a weak dark brotherhood in Elsweyr. It gets old redeeming a sorry guild each game. Heck, they must have been doing good in Morrowind's time or else Old Mournhold would not have been so dangerous.

From the lore there is only one sanctuary in Corinthe, but, even if it's hidden somewhere in, under or near the city, it is sufficiently well-established to be know from outside the province. And Elsweyr is a country always in war so I think you could easily find like a little army of assassins to hire in their sanctuary.
Khajiit are pragmatics. The Dark Brotherhood in Elsweyr should be more like a business than a cult but not to the point of having a shop!

I think it would be better to have the brotherhood in the city; not under it. That idea has gotten old with each elder scrolls game.

The Elsweyr Dark Brotherhood could make use of the Khajiit abilities and have a look more ninja-like than the others. They could use throwing weapons and illusions spells. Their sanctuary could be like a ninja fortress: look like a regular building but have hidden doors, sliding walls and secret rooms.
Everybody know where the sanctuary is but nobody know it's the sanctuary.
You could also imagine that there is assassins in disguise. When you are send in mission, you can contact some "hidden brother" to obtain stuff, information or help.

Sure. everybody in the building is a brotherhood agent. Just not dressed or portraying the part to the public. That is kinda why i suggested one of the fighting temples. It's the perfect front.

I second the idea of having NPC's who seem generic until you join the dark brotherhood. Perhaps an unlikely brother in torval has recently seen your mark...

So, how about a different approach to finding your mark as I said above? Perhaps you have to ask around town or even Elsweyr itself just to narrow down a location? (Here and there, just to break the uniform "go kill easily found mark, get paid" routine.) The Dark Brotherhood may be powerful and smart, but not every mark can easily be found before the contract is given.

Or a mark may know they are in deep and have gone to ground.

Being thrown in as second to a botched kill. And having the mark know the brotherhood is out for them. And have taken measures would be novel.

I meant NPC outside the sanctuary could be assassins in disguise.
Remember the first Assassin's creed? You have to find informations about the target by contacting other members.

And maybe even a few guards. Not a bad posting for an assassin in disguise.

My idea+Rattfink's+Grim's=epic and new Dark Brotherhood.

At least I hope they won't finish all dead at the end of the quest...

Nah, That's been done WAY too much.

We could also do the opposite. The Dark Brotherhood is near annihilated and only the master and some of his assassins remains. Others have fled or are hidden (that why you can find disguised assassins). You could even do a story about how they became like this and that explain why the psychotic bloody-handed khajiit is the chief (could be a bad thing as a good one).
You could also have targets who affect the activities of the guild. That could be optional side quests and when you progress you obtain new services, new members, the building is restored, etc...
As for Sithis, it's just an image used to convince and federate members. More a business logo than a cult. And to be coherent with the godly background, as the final reward, or in a quest unlocked after you become the new head, you could obtain the Mask of Sithis (which will fit the DB uniform) so the player, as the grand master, will become an avatar of Sithis.