So, I have a basic outline of a city for a Thief/Dishonored style game. It has - or at least I hope it has - the elements a game like this needs. Slightly more advanced than the Renaissance; no multitudes of non-human races; a mysterious ancient civilization for some mystery and to provide an excuse for artifacts/rare treasures/forbidden magic; and lots of dark, cramped alleyways, rooftops, waterways and underground tunnels. The next step is figuring out what a game like this needs in order to work.
There are roughly four groups of actions characters in these games take: sneaking around, taking down opponents, overcoming obstacles or puzzles, and stealing things. This applies even to modern or near-future games like Deus Ex: Human Revolution or Alpha Protocol. For the opposition, there are typically only two types of actions they take: looking for thieves and trying to kill them.
With that in mind, I can flesh out a rudimentary list of various abilities. They're intended to be their own skills, instead of stunts for existing skills. Some things that aren't on this list like Physique or Will may still be available when needed, but they aren't a key focus in this genre. Even so, a general skill like Investigation shouldn't be allowed to overshadow Case, which is intended on being a narrower, more focused skill so that it can concentrate on what's important to the genre. I'll detail each of these with overcomes, advantages, attack and defense later (with some possible additions and changes).
- Alertness - A measure of knowing what is going on around you. This is not much different than the existing Notice skill. Guards typically have this skill, which they use to blow your stealth.
- Breaking - This is the ability used for picking locks, opening safes, figuring out how to manipulate doors, hatches, gates, etc.
- Cant - This is a measure of the character's reputation and connections within the criminal underworld. It can be used to get information on potential missions, find employment, obtain equipment, or locate other less-than-lawful knowledge. It can also be used to communicate with other underworld types without Squares (i.e., normal people) understanding them.
- Case - The ability to find vulnerabilities and items of interest in a location. This includes guard patrol patterns; hidden or little known entries/exits; safe routes; hidden rooms; compartments or safes; valuables "hiding in the open"; etc.
- Deceit - This is identical to the default skill in Fate Core.
- Fence - This is the ability to evaluate the usefulness or value of items. It is also used to locate buyers or sellers. Thieves typically have a rank or two in Fence, but often rely on dedicated individuals.
- Fighting - This is the standard skill from Fate Core. Note that most thieves (and even many assassins) are not particularly good at it. Guards almost always have this skill.
- Pilfer - The ability to take (or place) objects without being noticed.
- Shooting - Another standard Fate Core skill. Some thieves and assassins prefer Shooting to Fighting, so slightly more have some level of it. Guards that don't have Fighting usually have Shooting. The worst ones have both.
- Sneak - The ability to avoid being seen or noticed - basically Stealth from Fate Core.
- Square - A measure of the character's non-criminal contacts, legitimate concerns and resources. It also be used as a measure of how honest or non-suspicious the character can appear.
- Takedown - This skill is used to quietly, and quickly, remove opposition. It is separated from Fighting to allow thieves to be good at taking out opposition but terrible fighters.
- Tracing - Also called parkour or freerunning, this is a particularly specialized form of Athletics dedicated to overcoming and navigating obstacles. This may not stay as a separate skill, but instead become an Athletics stunt (there is a good argument that the ability to do parkour means being generally athletic).
Player CharactersObviously, in a game like this thieves don't break into manors in groups like a stealthy flash mob (or a flock of crows - you get a brownie if you get the reference). For the most part, this genre is one of solitary characters. There are a number of ways to handle this - having a main character and a supporting character, or have players play different roles within the criminal underworld. Since we're assuming everyone wants to be the dashing Flynn Rider, We'll go another route. Each of the player characters perform their own missions and jobs and meet during downtime to take care of other business and drama. When a player character decides to take on a mission or job, the other players collaborate with the GM to flesh out the details. The other players also assume roles in running opposition against the player. This will require more work later on to determine exactly how the whole thing works.
GuardsThis is a genre where the opposition are kind of like Barney Fife until they are provoked. They are Fair NPCs, with no stress boxes and one skill (Alertness +1). But once they spot your character or otherwise become sufficiently alerted (like you accidentally blow something up) they become more like Jack Bauer.
This is simulated by guards, soldiers, etc. (and only those types of opposition) becoming Good NPCs once a certain threshold has been reached. They become much deadlier and more difficult to deal with at the worst possible time - when you are out in the open and exposed.
If there's a threshold which needs to be reached it's possible to have the player roll a contest consisting of obstacles and if they fail the guards are alerted. This option seems like a cop-out. Once the alarm is raised, there's no good way of figuring out how long it should last or what the consequences are. Consequences are probably the key word there, and where consequences are a possibility a stress track is sure to follow. Side note: Apparently I must be the stress track king, considering how many I use in Strands of Flesh and Spirit. I promise I won't go that far here.
Characters using the Sneak skill have a Stealth Track. This is a standard two-box stress track (there may be skills, stunts or extras that add to this). When a character fails a roll or otherwise does something where they might be caught, they can either take the stress or downgrade and take a consequence. This doesn't add any additional consequence slots, meaning the character is vulnerable in a physical or mental conflict because they have a stealth consequence. This is intentional - having the consequence of "I Found Him!" means more guards are going to be coming down on you and you're one step closer to getting run through (criminal justice in this genre doesn't often involve courts or jail).
Stress clears at the end of the scene, but obviously the consequences linger as per Fate Core. The recovery action required depends entirely on the nature of the consequence. If you have the mild consequence "I Know You're Here Somewhere!" you would just need to take an action to convince the guard that it was nothing, and then rename the consequence to "Damn Rats" or "It Must Have Been the Wind". Once that has been accomplished, it's a matter of not getting caught for the remainder of the scene so you can clear the slot. A moderate consequence might be "Set Off The Alarm", which will have to be disabled or turned off to downgrade to "Stay On Alert". A severe consequence might be "Botched the Bamford Job". Bamford is going to want to find the thief who infiltrated his manor and depending on how things went down or past history you might be a suspect. Contacts may not want you around until it's cleared up; worse, some of your more opportunistic peers might decide to help Bamford out in finding you. Once you run out of Stealth stress boxes, the guards know you're around (if they haven't seen you directly) and at that point go from being Fair to Good. That's when things unquestionably go pear-shaped, and it's probably best to try to get out of there as fast as possible.
Next up, I'll start to flesh out the custom skills.
For a lot of good references on 18th century London thievery, including a dictionary of Thieves Cant, a list of professions, business directory, costs of goods and other neat information head on over to this website.
Finally, I'd like to thank the Fate Core Google+ Community, particularly Jeff Johnston, Jack Gulick, Andy Hague and Andrew Jensen, for their terrific ideas on how to handle stealth.