Death Sword

Death Sword (ゴベラの剣, lit. Sword of Gobera) is the miniboss of the Arbiter's Grounds dungeon in Twilight Princess. The Death Sword is one of the few creatures, Poes included, that reveal their true form when seen through Wolf Link's finely tuned wolf senses; To human Link, the body of the Death Sword is invisible to the naked eye.

Strategy
When Link enters the room, the Death Sword is found embedded in the ground, bound by ropes. Cutting one of the ropes binding the Death Sword will cause the evil magic within the blade to awaken and burn away the rest, thus beginning the battle. Link must transform into wolf form and use his senses to see the Death Sword's master. When it attacks and gets its sword stuck in the floor, Link must jump at it and start biting to make it visible. Afterwards, he can shoot it with arrows while it is floating in the air to stun him. Alternatively, he can use the Clawshot or the Gale Boomerang to do the job. It then will fly in circles around Link, and finally attempt to strike him with its sword, at which point it will get stuck again, leaving its head vulnerable. Repeating this process a few times will put an end to the Death Sword, and Link will be free to claim the Spinner in the next room.

Theory
At the start of the battle, papers are seen dangling from the ropes that hold the sword down. If looked at closely, they appear to have ancient inscriptions written upon them. This may mean that the Death Sword was a demon from the ancient times. It seems that the people living in the Gerudo Desert were unable to defeat the demon (considering he is invisible to the human eye) so they sealed him in his sword. In terms of the sword, it seems that it was an object of Ganondorf's origin because at the end of the battle, the sword is the only thing to burst into dark energy, while Death Sword himself turns into a group of flies and exits through the roof. This may mean that Death Sword was aided by Ganondorf, and used to kill the people of the desert.