I agree with Mystic on this, it gives a good idea that a common language would exsist. In my world I do not have a common language but I do have a Traders Common which is a very limited form of communication existing of approximately 200 to 300 words that can be used mainly for trade and little else. Similar to Chinese Pidgin English except a bit more limited.
Different than I recall the conversation but it is still a unique and scary item to be had. An interesting plot, should the players try to infiltrate a new cult using this and see it work, how then would they react to seeing someone they know on its grill? A mad dash to save them and a large fight ensues in the midst of a few dozen cultist. Fun times.
Most of what I had planned on saying was said, although I disagree with Muro should I run this I would inevidably end up throwing the players or some of them into those who got arrested the night before and end up on the shopping block in the morning none the wiser for being from somewhere else. Kudos.
As a fan of magic of all kinds I love it when someone puts something detailed like this up. It is not extravagantly so but enough to wet the perverbial whistle. I agree with axlerose in that it seems more of a flashy thing that actual mechanic wise, but if they could somehow become a mechanic that made them unique without bogging down gameplay that would be wonderful.
And on a side note, I think the idea of Embuing is a grand idea.