With the exceptions of Faerie Dragons, Imps and Pixies, familiars do not speak common.
Edit: I'm too slow...
I recently received a Tell from a GM that many types of familiars could not speak, and that this was in the Lore somewhere.I've done a very thorough search of the Lore...
In Layonara, there are even special commands to support speaking through your familiar: "/o f".
Thought it's more likely the Eyeball would speak "Undercommon" or some other language and not "common"
We don't have an "undercommon" and most sentient Deep races speak Common in our lore.
"We don't have an Undercommon ear, so no character is ever going to be able to use that with an Eyeball familiar. Also, since most Deep races speak Common on Layonara, there's no reason to suspect that their familiars that are capable of speech would not also know Common, too, and since familiars aren't restricted by race, there's no reason Eyeballs shouldn't speak Common regardless of their masters' origins," rather than, "We don't have an Undercommon, period. Deep races have their racial languages, and most know Common, too."
For speech:Imps, Pixies, and Layonaran specific Faerie Dragons - Speak commonRavens - Despite speaking a language in D&D 3.0, they can't speak any language. Layonaran ravens do not have vocal chords. They emote-speak Animal.Natural Animals - Emote-speak the animal tongue. It would be up to a GM to allow communication between animal familiars and other natural animals of the same type, as in D&D 3.0.Pseudodragons - Do not speak common. Whether they speak an animal language, or draconic, is undetermined. They do not have the telepathy abilities in D&D, even with their master.Eyeballs - Presently undetermined, but they probably speak common.
For communication between Mage and Familiar:It is NOT telepathy!!! - Dorganath is very adamant on this pointThere is an empathic bond - Interpret the "What do you want me to do" menu you get for familiars that way.Communication as a non-speaking animal should be done as emotes
Possession is not telepathy. When a mage possesses a familiar, the familiar "becomes an extension" of the PC. This means if you scout an area as a possessed familiar, and then unpossesses (instantly transporting back to the mage), the mage knows everything because the mage was the familiar.Whether a mage can speak through their own mouth while possessing a familiar is undetermined.
Mages as familiars are limited to their mental abilities and their familiar's physical abilities. When possessing an animal familiar, a mage cannot speak Common for lack of vocal chords, and cannot speak Animal for lack of knowledge (unless she knows Animal tongue).
Other aspects of familiars:How a familiar manifests is undetermined.Whether a familiar has a separate existence anywhere when not manifested is undetermined.
What makes up a familiar's physical body (and how a familiar is able to resurrect after being "killed") is undetermined.
Whether the standard mage practice of "healing" a familiar by unmanifesting it and remanifesting it is ok in Layo is undetermined
Whether a familiar is a "true" example of its species subtype, or merely an artificial creation of the spell (for example, could you learn Infernal from your imp?) is undetermined.
Whether, if your familiar is not a "true" example of its species, a mage could create their own "species" of familiar is undetermined.
The specifics of the alignment restrictions presently default to NWN's loose (one diagonal move) limit. (As a TN, you can have any type of familiar you want, you aren't limited to NG/LN/NE/CN.)There are no CN and CE familiars.
I don't think that's mechanically possible, as the "Summon Familiar" functions only once/day.
The way I've always seen it is that "possession" is utilizing the link between mage and familiar to see through and direct the familiar. I've also always treated this as a "full-time" sort of activity, requiring one's full concentration to maintain it. That would imply that a mage cannot speak through his/her own mouth while possessing the familiar. This is somewhat mechanically enforced as well.
Familiars (and animal companions) are not "summons". They're terrestrial in origin.
This has come up before and the gist is they have the good sense to get away before they actually die, then go off an heal, making them unavailable to their master's call for a longer than usual time.
It's not a creation of the spell, and you can't learn Infernal or any other language from it.
Nope, they can't, at least not without some OOC approval and a WLDQ of some sort.