Formal language of the Erlyid
Developed from the language of the original Erlyid people who crossed the mountains from the east, High Erlyid is the formalised language of the Empire. The nobility of the Empire uses it in legal documents, diplomacy, and conversationally; inscriptions on monuments and public building are made in it. Most historical documents are written in it. It is a complex and rather strange language, and it takes twice as long to learn as any other.
The decline of the Empire in general has been paralleled by the decline in the use of the formal language, and it's now seldom encountered except in the Imperial heartlands, historical documents and formal legal agreements. Where people do still know and speak it, its' pronunciation is often imperfectly remembered.