Augustine Line

The Augustine Line is a circle of latitude that separates Arth into two hemispheres: North and South. Similar to the Apex Meridian, it is an imaginary line of separation used by travelers and cartographers to determine cultural, geographical, and ecological differences. When the two lines intersect, it lines up on Nil Isla, an island that disappears under the ocean once every fifty years, and after five years underwater it returns to the surface.
== Overview/History ==
The Augustine Line, discovered and named after famed explorer Traego Augustine over a millennia, has been used for centuries up to today as a method of map making as well as travel, due to it's disputed existence. Noting a definite change between land that is bordered by the line, scholars debate if the Augustine Line is not just an imaginary line, but is actually a real tangible physical split of the planet. It's origin is unknown, but considering it's recent discovery only one thousand years ago, the biggest theory is that it was caused by magical imbalance or overexertion during the War for Arth. 
It is also a measure used by sailors to determine how far they have gone, with many attempting to sail on the line, due to a legend. The legend states that if a ship manages to sail the entire Augustine line, then great treasure will reveal itself to them. However, no sailor has been able to sail on the entire Augustine Line and return.