Bellum

Bellum is an evil squid like creature who is the last boss in the The Legend of Zelda: Phantom Hourglass. He is defeated with the Phantom Sword. Bellum drains beings of their life energy, being the one responsible for the draining effects of the Ghost Ship and the Ocean King's Temple.

In addition to having an appetite for life force, Bellum created the Phantoms using his power, making them as invulnerable as himself to weapons outside the Phantom Sword. Bellum is also the Latin word for war, possibly meaning he is the god of war. Bellum's motives are never touched upon, other than sating its hunger for souls and destruction.

History
Later in the game, Oshus reveals to Link the monster known as Bellum. It is revealed that Bellum was an evil so powerful that he forced Oshus from the form of the Ocean king by feasting upon his life force until he was too weak to fight, and had to split his soul apart from his real body. It is also revealed that Ciela was split in two in order to protect her from Bellum who had taken upon himself to capture the Spirits, and was Bellum himself who was responsible for the terror of the Ghost Ship.

Bellum is revealed to be nesting under the Temple of the Ocean King, feeding off of the Ocean King's soul and growing underneath the earth and preying upon those who dare enter, as well as the victims of the Ghost Ship. After obtaining the Phantom Sword, Link delved into the deepest depths of the temple in order to face Bellum and save the Ocean King.

Battle
Bellum has three main forms, the first of which is his normal squid like appearance. In this form he drops the missing power of Ciela, after Ciela regains all of her power Link is given the ability to stop time for a short moment giving Link the opportunity to attack Bellum's weak eye.

The second form is where he is fused together with the Ghost Ship.

The last form is where he possess Linebeck transforming him into a large phantom. His powers are: teleportation, energy balls, toxic ooze, making monsters using the sand of hours, clone making, levitation and possession of others. Bellum is an excellent sword master as he is able to preform the tornado slash.