What do you do about the languages issue?

[Solan]

The Demiplane of Ravenloft rivals Europe for the number of different languages spoken. That's not much of an issue for native-born adventurers, but what of those brought here by the Mists, especially those only staying for the length a single module? How do you handle no one understanding them? Do any of the Ravenloft adventure modules deal with this problem, or do they just pretend everyone speaks Common?

[Rock of the Fraternity]

PCs could probably retrain a rank in speak language/linguistics.
Or they could 'pre-invest' a future rank in the same, gaining limited understanding at the price of having to roll Intelligence checks to make sense of things until they actually can invest the skill rank.
That, or they can muddle along using comprehend language and/or tongues as best they can.

Alternatively, you could decree Vaasi is close enough to Forgotten Realms-style Vaasan that people from the Forgotten Realms who know Damaran might understand it. Darkonese might be intelligible to someone from Oerth who's fluent in Oeridian.
Either keep drawing parallels to languages from other setting the PCs know, or leave it at that; Darkonese and Vaasi are two major languages that may help baffled Outlanders get around.

[Five]

There is a whole page dedicated to this in the Ravenloft Dungeon Master's Guide.

Optional Rules: Language Barriers

Three options provided are:

1. No change. Characters need to improvise. Sink or swim. This is considered the "default" option. But keep in mind the whole line of 3E products is following the trail blazed by Domains of Dread and is clearly steering away from the "Weekend in Hell" approach as established in the Black Box, and (arguably?) touched on later again in 5E.

NPC translators (another trapped outlander?) and magic are effective bridges, if a DM doesn't want to get bogged-down with the grit that comes with realism.

2. Local "Common". Characters Common is same as local domain Common. Great if you want to hint that the domain, and its dark lord, may originate from the same world/culture as the characters and in establishing a smoother landing for the players when they touch down in RL. Other domains fall under option #1.

3. "Common" is Common. Built around the Weekend in Hell approach to Ravenloft. Communication between PCs and NPCs are generally smooth, though private, suspicious and/or sketchy NPCs may speak behind the PCs' backs (or on-the-cusp-of-outside of earshot) in their native tongue.

[Solan]

Thank you both. I don't have the Ravenloft Dungeon Master's Guide, so I was unaware it addressed this problem.

[Five]

For some reason it's not available on DriveThru, but the Ravenloft Player's Handbook (3.5) is. Weird.

[IanFordam]

My players are odd in many ways (so is their DM, to be fair), but I'm lucky in one relevant oddity: They often enjoy roleplaying the language barrier. That gives me more latitude to tinker than I would have with a group that does not.

When running a Ravenloft adventure, I can usually talk at least one person into playing a native of the Land of Mists, and that PC becomes the linguistic and cultural translator for the party. From there it's down to figuring out if the other PCs' native tongues have any parallel-universe-convergent-linguistic-evolution similarities to any of the languages spoken in Ravenloft. For example, one person played an Outlander from an alternate medieval Paris (It's like France... but with werewolves!), so I decreed that he could fumble his way through High Mordentish or Souragnien. I've also started campaigns assuming that the PCs have been in their starting location long enough to have learned the rudiments of the local language.

On the other hand, I've also been known to take the easy way out. Circle of Darkness opens with a Vistana roping the PCs into the adventure. I had her hit 'em with a spell that let them comprehend Balok. By the time the spell wore off, the PCs had been in G'Henna for weeks and learned to speak the language for real. You see, as odd as my players are, they also want to be able to roleplay something other than the language barrier sometimes.

[Lord_Pruitt]

It's kind of a hand-wave-ish way to go about Languages, but I usually say the domain that they will be in mostly (at least at the start of the campaign) has a language similar to Common, then make adjustments from there.

[Mistmaster]

I use Baloki as Common.

[Mephisto of the FoS]

Voice of the City
For some, the ability to make oneself understood in the midst of any culture is of far greater value than the ability to influence the beasts of the wild.

Class: Druid, ranger, or spirit shaman.

Level: 1st.

Replaces: If you select this class feature, you do not gain wild empathy.

Benefit: Through a combination of body language, tone, and expression, the voice of the city can make herself understood by those who do not speak her language, and she can interpret their meaning the same way. Simple concepts that can be conveyed in a few words (such as "Help!" or "Drop your weapon!") can be conveyed automatically. More complex concepts require her to make a roll: d20 + her class level + either her Wisdom modifier (if trying to understand someone else) or Charisma modifier (if trying to make someone else understand her). Roll each only once per conversation. If she fails, she cannot try to communicate with that specific individual via this ability until she has gained a level. (Thus, it is possible, if she succeeds in one roll but fails in the other, to hold a conversation where she can understand the other speaker but he cannot understand you, or vice-versa.)

The DC of the roll depends on creature type and how closely the individual's language is related to any of her own. The ability works most effectively with other humanoids. In this case, if the individual's language uses the same alphabet as any language she knows, the DC is 20. If it does not, the DC is 30. (See Speak Language for this information.)

The above DCs increase by 5 if the speaker is a fey, giant, or monstrous humanoid; they increase by 10 if the speaker is an elemental. If the other individual is of any other creature type, she cannot communicate via this ability.