The ethereal mount is an exclusive reward given to accounts with at least 3 years of paid subscription and when equipped let's you ride a pet mount that can not be killed. These come in many different types and for different years. If you are interested in a specific one talk to live chat otherwise you will be given a random one. These are useful for always having a pet mount that you can truly rely on. Choose from all 5th year or less ethereal mounts.