Santa "GachaClaus" can only be admin tamed using the forcetame or dotame commands. They cannot be ridden since there is no saddle slot to equip a saddle though it still prompts you to do so. You can whistle command the GachaClaus but it will not indicate it is "obeying" as it does. Cryopods do work on them. The only way they will produce crystals after being tamed is by feeding them mistletoe or coal. They don't seem to suffer cryosickness since one did produce a crystal for me while under cryosickness.