if you put on necromancer robes/hood and walk into a cave full of necromancers, they should treat you like one of them. Same should go for other groups. It would even help to improve rping because if you wanted to rp a necromancer, you could just join a group of them. And vampires should be able to find a group like them as well

I agree, but I don't like the vampire idea though. A vamipre should be able to, if you are close enough, realize you are a normal human and not a vampire. But not all necromancers should be fooled by you, the ones who know how many and who is part of their group should realize you are not part of it.

you should be able to talk your way in though. And for vampires, i meant if you WERE a vampire you should be able to join a group of them..i should have clarified that because i didnt mean that one as a disguise

I agree that costumes should lower hostility initially, but that suspicion clould still exist, and that the ruse could fail upon closer inspection by a high ranking NPC (like a high-priest, or Army Sargent, or guildmaster).

I don't see the role playing aspect of just loitering around necromancers... That should make them very cagey and paranoid unless the game specifically supports dialog that allows you to join their group.

Which should be pretty much all of them, logically. If they didn't know who you were, then they would challenge you to prove you actually were a Necromancer. So all in all, I don't really see that ability as being all that practical, it would probably be too much hassle to work into the game.

Interesting ...

Let's say this we have Guild A ... Guild A have as clothing 'Green Tunic's ...

We have also a Guild B .... Guild B have as clothing 'blue tunic's ...

Both guilds aren't on good therms with each other, no they are atleast unfriendly or hostile ....

You walk with you blue tunic in Guid A (the green tunic guild), you aren't even allowed to enter the building and if you do so ... People are outright hostile towards you ...

The Heretics and Zealots in the Shivering Isles already did this,

Do me mind to notice that Morrowind did have such system if you wear in Imperial Legion and you don't wear you Uniform in the Legion it self they were saying 'Why don't you wear you uniform', and stuff like that .... Even before starting to talk to the NPC If I remember correctly ...

It is for me pretty strange that the Mages Guild in Oblivion hates the necromancer guild but you can just walk with you Robe into a guild hall or even in the university without any problem .... Yes I know you can;t really talk to npc's like that , but other than that they don't care at all ...

They should atleast turn hostile towards you or call the Battlemages ...

IMO... All NPCs should have attribute scores, and the game should poll the relevant stats to determine if that specific PC sees through the ruse; and then have them able to inform other NPCs (meaning to keep the ruse, the PC must deal with them in some way).

new vegas did this fairly well. normal run of the mill faction members could be fooled if you wore their outfits but the faction leaders and certain guards would recognize you. it made sense because a guard is going to be more familiar with people coming and going and the leaders have to deal with their underlings all the time so they would be more likely to recognize an imposter. i hope they keep this in skyrim cause it was kind of nifty.

Also, the sneak and social skills should improve your chances of not getting caught, or talking your way out if you are suspected.

Well I was thinking only high ranked members should realize you are not part of them.

But putting guard uniform on should work, as long as you don't get too close to someone or do somethign strange that a guard wouldn't do.

I hope that we can have something similar to the Gray Fox's Cowl where you can commit all your crimes with that and when you take it off, nobody knows that you just raided an entire city.