Hat of Disguise - how to adjucate it well

[Maitre Du Donjon]

Hello all, i'm starting an evil FR campaign friday, and all 3 of the characters (i'm the DM) will posess hats of disguise (they all started at level 9). I just want to be sure that the players can use their gear to maximum efficiency, without giving them absolute power of law-evasion (did i mention its an evil campaign? i did? then did i mention that the 3 characters are a rogue/guild-thief, a rogue/assassin and an invoker? i did as well? in another thread? thats right)

First of all, do the effects of a hat of disguise wear off or once a disguise is chosen (lets suppose for now its a general disguise) is it somewhat permanent (until dispelled / cancelled by the user / seen through)?

Should I impose limitations on the number of diffrent disguises the players will be able to take?

What sort of interaction would warrant a saving thrown from someone the characters are interacting with? Combat, of course, and any sort of touching, but what else?

When should i treat the change self as a disguise? Lets say the thief (who is an elf) robs an inn and the patrons see him. He goes into the backstore (alone) and uses the hat to look like an old dwarf, and leaves the building through the back door. If the patrons came out, would they get a spot check vs the thief's disguise check? What about guards who have not seen the thief but are now facing the dwarf?

I know i'm going to have some troubles with these items (but i don't want to take them out of the game) and any info, general or specific, will be gladly appreciated...

Maitre D

 

[Elder-Basilisk]

What kind of action would warrant a saving throw? Touching the character or combat obviously. Also, if the character is makes too much or too little noise or appears to be moving the wrong speed for the clothes he appears to be wearing (ie a character in leather who looks like he's wearing fullplate strolling down the feet at movement 30' will look and sound rather obviously odd. Similarly a character who's really weaing fullplate or a chain shirt attempting to look like an urchin in rags will look and sound odd clanking down the street at a movement rate of 20.) While characters might minimze the sound created by armor by moving silently, this will slow them down too much to look appropriate (1/2 movement or take a penalty) and they will look like they're moving silently (which is clearly a much more careful kind of step than the carefree manner a person may normally walk in). There's not too much non-magical that could be done to sound like you're wearing fullplate when you're not either.

As to the disguise check. Roll it as soon as the character makes the disguise and then just assume that all common people and guards are taking ten on their opposed spot; you might want to roll for guards who are actively looking for the thief (remembering to add in penalties to the disguise for appearing as a different race and the limited alterations in apparent size the hat can make--it's not enough to look like a halfling). If the character failed then obviously he did something wrong and his "dwarf" doesn't look right.--for instance he bangs what appears to be his shoulder into the door and starts grabbing his elbow or he colored his hair red but forgot to make the illusion give him a red beard. Everyone should have a chance to spot that there's something funny about the "dwarf"--even if they have no reason to suspect his real identity.