Stamtaal is a regional dialect native to the nation of Perrenland.
Stamtaal is not really a different language to the Overking's Common, though it usually sounds like one to outsiders at first. It is characterised by some elements of pronunciation, grammar and vocabulary drawn directly from Flan.
Most foreigners who are able to speak the common tongue struggle to understand Stamtaal initially. It roughly takes a month for a visitors to be able to speak Stamtaal reasonably fluently.