The Seablade is the main magical weapon in the Aquatic Kingdom Hearts story series. It is wielded by the one called the Seablade Bearer, the One Who would bring balance to the Three Hearts of the Sea. Passed down from one bearer to the next, its latest owner is the hero of the stories, Eric Thatch. It has recently been passed on to his daughter, Melody.
The Seablade is usually used in fighting, but it has many other abilities. The most important ability featured throughout the series is the ability to govern the 3 Hearts of the Sea. The most apparent use of this ability is in in keeping the balance of the 3 Hearts, as well as using the powers of Ice and Water. It also can transform into two Blades, and, of course, be used to defeat the enemies the present themselves throughout the series.
As the name implies, in combat, the Seablade is used in a manner similar to a sword. Despite being a powerful magical artifact, the sword makes an efficient combat weapon, and is shown to be a particularly effective weapon against the opponents. However, as a downside to this, the Darkness can sense the Seablade as a homing beacon, and thus the Seablade wielder is at constant risk of attacks at any time.
In the past, past wielders are able to extend the Seablade's length with Light or Darkness for its ultimate attacks.