- A creepy sword received from Alice. Made from 666 melted angels, it can seal monsters.
- “That's the cursed blade, Angel Halo. The original fallen angel created that in order to bring ruin to the angels.” - Valkyrie
The Angel Halo (エンジェルハイロウ) is a special weapon wielded by Luka, replacing his Iron Sword (although he still keeps his former weapon). It was created by Lucifina as a key item in battling against the angels and Goddess Ilias herself. Luka finds the weapon extremely grotesque-looking, describing it as “evil”, self-implicating as a villainous person for its wielder, and “looks like [the angels are] being tortured”. It was given to him by Alice XVI (Sixteenth), noticing he has problems fighting to his fullest. Alice says it is the only one of its kind in the world.
The sword eats away the magic of whatever it slashes, allowing it to weaken and seal creatures by distorting their physical form (e.g. an Earthworm Girl changes into a normal tiny earthworm, an Elf shrinks, etc.), although they can return to normal once they have accumulated enough power or are unsealed by a more powerful being. Alice also mentions that because it was forged from angels, it can be used against and even harm them, reducing them to their original holy state; this makes it perhaps the only weapon with which a human or monster can injure an angel. The Angel Halo also makes eerie noises, which Alice says is expected due to the nature of the weapon's creation.
Lucifina, who expressed doubts about Goddess Ilias ever since she initiated the Great Monster Wars, created and delivered the Angel Halo to Heinrich. Once he defeated Black Alice, the Monster Lord in his era, he realized his true enemy, Ilias, and revolted against her. Using the Angel Halo, he slew hundreds of angels and severely decreased their population, gaining the nickname "Angel Killer", before going insane and eventually becoming consumed and eroded by their holy energy. Ilias then stripped Heinrich's soul from the weapon and sealed it away at the Sealed Sinner’s Prison. According to Torotoro's blog, the Angel Halo was then sealed at an undisclosed location but was recovered by Tamamo.
Luka receives the weapon from Alice after leaving Iliasburg. He questions the sword's grotesque appearance and the eerie noise it makes, but once he uses its power against an Earthworm Girl that appears shortly afterward, he acknowledges its ability and thanks Alice.
While fighting Ghost Girl, Luka is pleased that the weapon can hit a being without a substance, but quickly retracts his statement due to the sword's creepiness. On cue, the Angel Halo then makes an eerie noise.
When Luka reached the Sabasa Kingdom, a guard noticed his sword. Luka immediately assumes that the Angel Halo just got him into trouble, although the guard assures it isn’t like that.
As Luka begins to leave the Sealed Sinner’s Prison, the Angel Halo momentarily shines with light, seemingly reacting toward Heinrich’s spirit.
While fighting Cupid, she is shocked that Luka's attacks hit her. Valkyrie states that the original fallen angel, Lucifina, created the Angel Halo to counter the angel race, who are immune to anything but holy energy, and warns Cupid to be careful.
Alice later admits that she used the Angel Halo to attack Goddess Ilias when she descended to give her blessings, inadvertently ruining Luka’s chances of becoming a "hero". Although Alice managed to scar Ilias, Alice was easily defeated.
When Luka and Alice inadvertently free Heinrich from the Sealed Sinner’s Prison, he reveals that he did originally use the Angel Halo to combat against Ilias and her angels, but the sword’s holy energy eventually consumed him and thus died out of his recklessness.
Tamamo later confirms Alice’s and Heinrich’s stories of their use of the weapon, also stating Heinrich received the sword from a fallen angel and had it from the beginning of his journey.
- 666, the number of angels melted to create the sword, is a reference to the Number of the Beast, often associated with the Devil in Christianity.
- Luka’s attacks during Granberia’s third battle cause her to bleed. According to Torotoro's blog, the sword is capable of killing if the wielder desires such, which also explains how Heinrich vastly reduced the angel population with the weapon.
- According to Torotoro's blog, Lucifina created the base of the Angel Halo. The weapon's current shape and appearance are the result of Heinrich using it to massacre the angels.
- According to Torotoro's blog, a being that is sealed by Angel Halo can only be restored by another being of equal (or greater) power to itself.