The Kyōkai Kyōkai no Mi as its name implies grants the its eater the ability to manipulate boundaries, more specificly the boundaries the exist between two points. The user is able to rend the boundaries betwixt those points, enabling them to apply a varity effects, be it manipulating the space between said points making it appear that a leagues worth of distance is only a few steps away. The user may also apply this effect in resverse, making a short distance appear to be a fortnights worth of travel.
Aside from the aformentioned applications, the Kyōkai Kyōkai no Mi also grants the user the ability the either reinforce or compleatly obliderate the boundaries between dimensions granting the user access to what is known as "Hammerspace" allowing them to seemingly prodouce a multitude of objects out of thin air, giving one the ability to overwhelm opponents with sheer numbers. However Auberon himself has stated that these objects come from a massive vault crafted by an ancient civalization in the sea floor, meaning the while this aresnal is large, it is infact not infinite.