Let’s think a little bit about languages. So in Sartar pretty much everyone either speaks Sartarite (aka Heortling) or Old Tarshite as their first language. Pretty much everybody also some knows Tradetalk – when you talk to someone you don’t know, it is usually in Tradetalk. Most people also know their cult language – usually Earthspeech or Stormspeech. That’s the language cult ceremonies typically employ.
A smattering of people know a foreign language such Praxian, Darktongue, Pure Horse Speech, Beastspeech, New Pelorian, etc. Esrolian is a closely related language – most Sartarites can understand Esrolian reasonably well, and some study it to speak as well as a native.
What language people use depends on context. For discussions with family, clan, and tribe, most people use Sartarite. At the market or with strangers, most people use Tradetalk. In cult rites, the cult language is often used (note – some cults have no special language). And foreign languages might be used to have a deeper communication than with Tradetalk.
So if you go to a marketplace, you will hear a lot of Tradetalk, some private discussions in Sartarite, and a smattering of foreign language (the trolls speaking Darktongue among themselves, the Seven Mothers cultists exchanging New Pelorian, etc.). You might even hear a curse or two muttered in a cult language!
Where do the old Pelorian languages fit? There are a whole host of Pelorian Farmer Languages – Darseni, Naverian, Kostaddi, Darjiini, Jarasan, Suvaran, Pelandan, etc. They all come out of Fire Speech (now only 1/10th skill) and most have some intelligibility with Dara Happan (1/2 skill).
I don’t think there are any common languages in lowland Peloria that are derived from Earthtongue – beyond Earthtongue itself (which is used by some cults).
New Pelorian is a newer development. It is mutually intelligible with Dara Happan and the other Pelorian Farmer Languages, and has some traces of Fire Speech and Pure Horse.