The Languages of Erebus
In the Age of Magic, a common language was spoken by all humans, with occasionally rather major dialectical difference (like modern English), and extensively used in interspecies communication (still like modern English). This language was known as Patrian. Dwarven, Elven and Orcish were completely separate languages, with no common denominators whatsoever, based on development from an entirely different mother source.
Angels and Demons, while their voices are easily recognised by their sound and timber, have no defined "language" of their own. What you hear, is your own tongue, spoken perfectly, if a bit oddly. What they speak between eachother, is known only to them.
The Age of Ice forced a separation of the Patrian language, with each nation having 1000 years to develop their own dialects of Patrian into entirely separate languages, formed, to a large part, by their culture and environment. The result is that few nations understand more than a few words of eachother's tongue anymore. In many ways, this is similar to the development of Norwegian dialects, where geographic separation led to some dialects almost turning into separate language, and the effect of Elven, Orc and Dwarven in some places is similar to the effect that Danish had on Norwegian, stronger in centres of government, weaker in the more rural areas, weakest in the remote valleys and fjords. That's just a note on inspiration.
On to the tongues as they are today:
There exists a Lingua Franca also in the Age of Rebirth. It is roughly similar to the original universal language, but has been changed by 1000 years of separation and the effects of new languages. Among other things, there is a lot more Elven and Dwarven in the new language.
Elven
Both the Svartalfar and the Ljosalfar speak the exact same language. There are no differences at all. Elven is what you might call a "strong" language. It effects other languages quickly and heavily, but Elves, being rather chauvinist, aloof and elitist by nature, never, ever feel the urge to adopt human linguistic traits or wording. They feel their language is perfect, and as a result, it doesn't change just because it is used by one or the other faction. Naturally, it didn't have any more trouble surviving the Age of Ice than the Elves did (meaning a lot of trouble, really, but not as a language).
Orc
Orcs have no illusions about the perfection of their language, stealing like crows, and breaking the stolen words, cadences and other traits of those they encounter and battle into a verbal shape that they are capable of pronouncing, rendering most of it practically unrecognisable. The once-proud orc tongue is thus only spoken by a select few, priests, shamans and the like - the rest speak a rather distressing and remarkably ugly pidgin.
Khazad
The Dwarven tongue of the Age of Magic remains rather well preserved among the Khazad. It has undergone some of the changes one might normally expect from a language in continual use for centuries, but due to both relative isolation and the rather conservative nature of Khazad culture, it has been changed far less than one might expect. A Khazad of the Age of Magic and a Khazad of the Age of Rebirth would be perfectly capable of conducting a simple conversation.
Luichurp
The Open-Skiers were heavily effected by human in the Age of Magic. In the course of their isolation in the Age of Ice, the Dwarven and Human tongues merged into a language that was entirely Luichurp-specific. But it is not in the Luichurp's nature to stick stoically to their guns. Extensive trading with other nations in the Age of Rebirth has tempered the Luichurp creole with a strong tint of the new lingua franca, something that sets them apart from most others, who exclusively use it in foreign relations.
The Humans
Elohim
The Elohim language is the Rebirth tongue that is closest to the universal tongue spoken in the Age of Magic. This is closely connected to the way the Elohim survived the Age of Ice, as both an organisation with a constant influx of new people, allowing the oddnesses of dialects to be balanced out, but also their role as the tradition bearers and protectors of the old knowledge. The Lingua Franca of the Age of Rebirth is heavily modeled on Elohim.
Sidar
The Sidar are extremely good at picking up tiny changes in pronounciation, inflection, intonation, body language and a host of other elements of communication. Many of the Sidar begin as artists and sages and are slowly changed from the intellectual language of their craft to more consise and less emotional speaking patterns. Thus, their spoken language has no need of being very complicated, beautiful, or expressive. A few words will generally suffice. At a few hundred years of age most of the Sidar have reduced their speech to a few words, which aren't shared easily. Beyond that the meaning of the Sidar is usually inscrutable to those from other empires, but they carry great wisdom and importance if they are understood. Those few words that are used to a very large extent the same as those of the Age of Magic's Patrian - however, they do not hesitate to pick up other words that suit their style of communication particularly well. As a rule, these words spread like wildfire, almost instantaneously adopted by all Sidar.
Sheaim
The Sheaim language is, in fact, engineered by the Sheaim leaders in such a way that the sum of all people speaking Sheaim across the globe is a ritual, the chanting for a spell whose purpose is unknown to all but a very few in the closest circle around Os-Gabella. As a result of this careful balance, the Sheaim language needs to be constantly tweaked and changed in subtle ways, to take into account the constant headaches caused by other languages affecting Sheaim, an increase in speakers, and not least Sheaim words being adopted by other languages. Even a surfeit of incorrect pronounciations can cause problems, so correct language is rather strictly enforced, both physically, magically and psychologically.
The Calabim
The Calabim speak two different languages, both derived from human speak. The vampire aristocracy speak a far more elaborate and elegant language, with a stronger influence from the original language. The people speak a weak and simple dialect, so atrophied by lack of education that it is hardly understandable to outsiders.
The Amurites
The Amurites speak both "High Amurite", which is closer to the original language of the Amurites as effected by the presence of Kyorlin, and "Low Amurite", a creole of languages based on high Amurite, but strongly affected by the many who flock to learn Amurite magic.
The Grigori
The Grigori, more than any other, are strongly affected by the many newcomers, who flee the oppressive reign of the priests, gods and religions. Grigori is, in many was, the English of Erebus, constantly undergoing change through the adoption of new words, altering them to make a seamless, flowing and evolving language. The Grigori are particularly noteworthy for their very interesting swearing, which is devoid of religious connotations.
Balseraph
The Balseraph tongue is reminiscent of Cockney rhyming slang - it is musical and quick-flowing, playful, inventive, constantly evolving, and purposely completely obscure to outsiders, even though the words used appear to be the same on the surface.
Kuriotates
The Kuriotates are a very large and sprawling nation, but with centralised rule. Like in France, this language is one of the main things that bind the nation together. Thus, there is a very strong adherence to it, and a firm, but kind, drive to keep it as pure and uniform as possible. The language is unique in that it has strong effects from Centaur, a language dissimilar to the other languages of Erebus, and in an inexplicable hissing intonation on the S'es.
Lanun, Hippus and Doviello
These languages share two very noticeable traits: they are heavily influenced by the preferred geographical environment and the cultural peculiarities, and there is an enormous variety of sub-dialects, understandable to eachother, but often quite remarkably different. The languages have also changed more than most away from the original language, making it hard for diplomats to speak the new universal tongue without their own tongue affecting it.
Illian
Mulcarn had dreams of creating a new world language from scratch. Illian retains much of his efforts, but also a lot of the old human, changed in much the same way as with the other nations.
Bannor
Very large incidence of Orcish and Doviello words, very rigid in basic form, but with a lot of space for new words. Sparse and precise, as befits a militaristic nation.
Malakim
Desert dialect, heavily influenced by elven. Fluid, easily shifting, like the sand they come from. The Malakim are very open and direct, not to mention deeply pious, aspects which are reflected in the language, not unlike Arabic in its constant invocation of the deity.
