So, one thing I don't like about most fantasy settings is the language "Common". Some settings describe it as a trade language, whilst others as a unifying language that all people speak. No matter how they describe it though, it is mechanically the same; a language that absolutely everyone speaks, to get past the fiddling around with not having a common language.
To me however, it feels like laziness. What is the point of all of these rich and varied languages based on race and geography, then completely negating the need for them. Sure, having a doorway inscribed with elvish script can be nice flavour, and a warning sign in druidic can have some affect on an adventure, but there is little real effect.
So, for Broken World, I have decided on a slight change. Common in this setting is called "Polyglot" and is a mix of many different languages. It is a true "trade language" in that it is mostly used for trade and when no true common language exists. You can communicate through Polyglot, but complex ideas and instructions are hard to convey in a language usually designed for basic trade discussions between two merchants. Here is an example of what I mean:
First discussion between two merchants that speak Imperial:
Menthar: "Greetings my friend! I see you have Chenar fruit from Quesaras available. It must be difficult to keep them fresh on such a long journey, yes?"
Bonare: "It is indeed. However, we managed to convince an elven druid to do one of their little tricks and the fruit has remained fresh and will continue to do so for another week. Of course, this was an expensive option, to keep this fruit in pristine condition....."
Menthar: "Good fortune. I may have a buyer interested from the Quesaran embassy. Perhaps you would like me to act as middle-man for negotiation? For a small fee of course."
Bonare: "My good friend, If you would be so kind, of course I would be able to compensate you for your time. After all, there is a chance that I could bring more in future, and no one loves Chenar more than the Elves after all."
Same discussion using Polyglot:
Menthar: "Hello. Chenar fruit look good. Fresh?"
Bonare: "Yes, magic fresh. Stay fresh more weeks. Expensive."
Menthar: "Good Good. I know buyer. I come back with offer?"
Bonare: "Okay. More fruit may come."
In the first instance, we can see not only has the sale been discussed, but also a future trade deal has begun to be discussed. In the second instance, a deal for the shipment is discussed, but little else due to the limits of Polyglot.
In mechanics terms, Only being able to communicate through Polyglot has the following penalty to skills:
Bluff and Sense Motive: As these skills are in direct opposition, there is no negative to these skills, as both simply cancel each other out.
Diplomacy: Diplomacy is a complex skill, and relies on understanding exactly what everyone wants, needs, and the subtle interplay of language. Diplomacy relying on Polyglot is at a -4 penalty.
Intimidate: Though language dependant, a great deal of this skill can also be non-verbal and blunt. it suffers a -2 penalty.
Perform (orate): It is incredibly difficult to perform this skill effectively in Polyglot. this skill receives a -4 penalty.
In addition, and spell, power or effect that is listed as "Language dependant" that uses polyglot may add a bonus to the target's will save, depending on the complexity of the effect. This is determined at the time by the DM.