The Grim Butterfly (妖霊蝶, "Ghost Butterfly") was a demon of alien origin and the true form of the Grim Comet. It was one of the main antagonists of Hanyō no Yashahime due to being the central drive of its plot.
The Grim Butterfly bears a great resemblance to the Dream Butterfly, except considerably larger in size, being as large as a castle. It glows in a radiant, rainbow-like glow most noticeable from its massive wingspan. Although seemingly an organic creature from the outside, its interior is bizarrelly more resemblant of an human-made structure coupled with furniture and even a library. Whether this is its true interior or molded by its hosts is unknown.
The Grim Butterfly seems to be a mindless creature with no objective or desire that is openly known. Even though its existence has tormented the world through a constant flood of Yōkai due to the Grim Comet, it hasn't shown any open hostility and is mostly a side effect of its floating cocoon and its pieces drifting in space. Thus any malicious intent is hardly discernible as it merely causes chaos as it normally travels with little control of its own.
The Grim Butterfly is even shown to be rather docile and easily influenced as it obeyed the commands of Rion and Osamu Kirin and assimilated both of them. It is through these two, mostly Rion, that the Grim Butterfly acts with an actual desire.
Diving right in the very heart of the Grim Comet itself, Osamu Kirin had noticed it deep within and immediately realized that it was the true form of said comet.
The Grim Butterfly is an unfathomably powerful demonic being. Mere fragments of its outer shell were filled with an abudance of Yōkai and plagued the world for centuries. Were its central cocoon to fall to Earth it would cause a cataclysm that would have humanity destroyed by the sheer amount of Yōkai that would come from it. Kirinmaru sought to defeat it, which would according to him would undoubtedly make him the strongest, a testament to its power. Osamu Kirin believed it could utilize its power to wipe every Yōkai from existence and rule the world with it, meaning it is capable of one-sided slaughter with no opposition.
- Miasma: The Grim Butterfly could exhude almost limitless amounts of miasma, so vast and thick that they made one of the layers of its outer shell, and can even regenerate it.
- Demon Power: Equally vast is the Grim Butterfly's demonic power. It was so incredibly powerful, that not even Towa could fully absorb its power through the Zanseiken. Conversely, it was capable of vastly increasing her power to the point her own boosted technique could dispel the layer of demonic power that protected its shell. This evidences the only thing sufficiently powerful to stand against the Grim Butterfly is itself.
- Thread of Fate: The Grim Butterfly is capable of utilizing threads of fate. These can be used to attach itself to potential hosts allowing them control of the entity. It also allows its hosts to achieve a form of immortality as Osamu Kirin declared to be immune to destruction from Kirinmaru's demise so long as he remained attached. Several multicolored threads can also be conjured and used offensively and are extremely sharp and durable. Nothing short of the Yukari no Tachikiri or sacred arrows will work against them.
- Demonic Absorption: The Grim Butterfly is capable of disintegrating other yōkai and absorb them through its wing powder. This seemingly only works with lesser yōkai.
- Demon Power Nullification: The Grim Butterfly can somehow reject demon nature attacks as Inuyasha's Kongōsōha was ineffective. There might be some limitations as Inuyasha believed the Meidō Zangetsuha to be effective, although unproven.
- Longevity: The Grim Butterfly has potentially unlimited lifespan as it drifted in space for hundreds of years while it was still in larval stage.
- Pocket Dimension: Contrary to its organic exterior, the interior of the Grim Butterfly is more akin to a human-made structure, filled with furniture. It even has a room resembling a massive library inside. Entrance to the Grim Butterfly itself is granted through a portal opening in its body. This likely means that the Grim Butterfly is in itself an interdimensional being.
It initially appeared as a wide pale blue glowing martial. It later turned a pinkish red as it got closer to hatching. The Grim Butterly itself has a black head with hot pink beady eyes, black antenna, black legs, and violet back. It's body glows and it's wings are neon colored with black on the outside and the veins of the wing are also black. It's insides are purple and slimy, but it's core resembles a temple with wooden floors, ceilings, and walls. It has wooden shelves with glowing orbs, and purple carpet.
- At the end of Resonance, the first half-cousins are seen confronting a big black butterfly surrounded by a blood-red sky.
- Similarly to Naraku's giant form, this gigantic creature places a major role in the big battle of the series.
- It bears a passing resemblance to the kaiju Mothra and Battra.