Kaiyo Kabe was a sea fortress that guarded part of the Myre's coast. It is an ancient fortress that guards one of the few locations that is safe for a fleet to attack from.
Kaiyo Kabe is an ancient fortress formerly commanded by Fujikiyo. Due to how unstable the ground is in the Myre, there are only a few safe places an attacking fleet can make landfall. In response, a fortress was built at that location. It is one of the few Samurai structures that have remained standing over the years. The fortress serves as a deterrent for enemy fleets, equipped with hundreds of archers and dozens of catapults to annihilate enemy fleets. Massive wooden spikes are also hidden under the water to destroy ships that get too close.
If attackers succeed in making it past all that, they can close the gates and trap the attackers in the bailey.
Since the arrival of the Samurai, Kaiyo Kabe has served as the Myre's defense and deterred attacking fleets. Unfortunately, its effectiveness ultimately became its undoing. It was so effective at deterring fleets that it would not face a real attack for hundreds of years. When the Vikings attacked during The Great Raid, it was unable to stop the assault.