Ernst Wagner is not a widely recognized name in the art historical canon, and without specific dates or context, it is difficult to provide a detailed biography. There have been various individuals named Ernst Wagner throughout history, some of whom may have been artists, but none have left a significant mark on art history to warrant an extensive biography in the general reference works. If Ernst Wagner is a contemporary or lesser-known artist, there may be limited information available about them. It's also possible that Ernst Wagner could be confused with other artists who share a similar name. Without more specific information, such as a full name, nationality, period of activity, or a particular art movement they were associated with, it is challenging to provide a detailed biography. If you can provide more details or context regarding Ernst Wagner, I would be better equipped to offer a biography that is accurate and comprehensive.