AT Monsters question.

My situation is like this: I play offline due to work-related issues(working at sea, no internet conexion for online play). I downloaded the game in September(5 or 6 to ve more exact). At the moment, I am HR 74. When do AT monsters appear? I remember that they were from events but at some point they were made permanent. Do I have to fight them whilst online from the event quest or they are already unlocked?

Many thanks ❤️