Lullaby

Lullaby (呪歌 [ララバイ] Rarabai, lit. Cursed Song) is one of Zeref's evil creations and a Living Magic spell. It served as the one of the villains of the Lullaby arc.

Appearance
Lullaby has two forms and thus, two appearances. It has it's initial and default Flute Form and it's Demon Form.

While in flute form it can't speak or move and its size is nearly 50 centimeters in length. It is probably made of wood and it has a skull with three eyes on one end. There is an oval-like cutout in the skull's brow. On the other end there are root-like cutouts.

When the flute transforms into its demon form. It becomes an extremely tall beast that has three eyes, two legs, two arms and one head. There are many cutouts in its body.

History
The flute was once just a tool for "murder by curse" at first, which means that it curses the target and causes it to die. After getting into dark Mage Zeref's hands, he further developed it into a Magical flute, called "mass-curse murder magic" that is capable of putting a death curse on everyone who hears its melody except for the Caster.

Magic and Abilities
Sound Magic: Lullaby has the ability, while in flute form, to be played. When it is played, it produces a song that, if heard, will cause everyone, not including the caster, to die.

Lullaby arc.
Erigor hoped to use this to kill the Guild Masters at their meeting. As Kageyama failed to carry out the mission due to regret for his actions, Lullaby transformed into its demon form to feast on souls. However, Natsu Dragneel, Gray Fullbuster and Erza Scarlet were able to easily defeat the demon flute. It currently is in the Council’s hands.