The Khitan large script was one of two Khitan writing systems used for the now-extinct Khitan language. It was used during the 10th-12th centuries by the Khitan people, who had created the Liao Empire in north-eastern China. In addition to the large script, the Khitans simultaneously also used a functionally independent writing system known as the Khitan small script.
More information on the Wikipedia page .
See also Khitan small script.