Lullaby exists in two distinct forms with completely different appearances and capabilities.
In its default Flute Form, Lullaby is essentially immobile—it can't speak, move, or act on its own. The flute measures around 50 centimeters long, with a skull head featuring three eyes and an oval cutout across the brow. The other end has root-like protrusions.
Transform it into Etherious Form, though, and it becomes a towering beast with a humanoid build: two legs, two arms, one head, and those same three eyes. Its body is covered in various cutouts and gaps.
Originally, Lullaby was designed as a straightforward murder weapon—a cursed flute that would kill whoever heard it. When Dark Mage Zeref got his hands on it, he weaponized it into something far worse: Mass Murder Curse Magic. Now the melody doesn't just target one person; it death-curses everyone who hears it, with the sole exception being the caster themselves.
Content compiled by AnimeList.moe from publicly available sources.
