Masteria Expansions, Names and the proof for each

 Isle of Vigilance, maybe?

Since this is a map, we can safely assume that North is the top of the image and south is the bottom. Thus, the bottom of the map is the Southern side of Masteria, and NLC is on the south coast. Taggrin explicitly states that the Isle of Vigilance is off the northern coast, so it's probably not on the map.