Illuminations allows Rimbaud to create a hyperspace, which is a completely isolated sphere outside the normal space that he has full control over and has different dimensions from the physical world. Initially, the ability had been shown to take the form of small, cubic hyperspaces that can restrain individuals among other purposes. In truth, aside from such forms, Rimbaud can alter his hyperspace's ranges accordingly, capable of generating hyperspace massive enough to cover an entire shipyard higher than its roof.
One trademark and unique trait of Illuminations is its highly impenetrable defense. Osamu Dazai once remarked that gunshots, explosives, and similar-level armament could not damage the hyperspace. Additionally, natural forces and elements like fire, thunder, lightning, light, and sound pressure cannot jump into the hyperspace. Aside from the fact that only Rimbaud can allow entrance of targeted people and beings inside it, the hyperspace also contains a thin film that acts as a cover for his skin, in which no physical contact can go through.
One notable entity that challenged this capability is Arahabaki, which was once able to penetrate Rimbaud's hyperspace defense during the explosion years ago due to its mysterious and insofar unexplained power. Nonetheless, Rimbaud quickly rebuilt his damaged hyperspace, allowing him to eventually survive Arahabaki's black flame that created a two-kilometer-diametrical-wide crater.
Illuminations can also turn people into abilities, even capable of resurrection to an extent. Specifically, Rimbaud can bring living humans or corpses to his hyperspaces and turn them into ability users. However, only one corpse can be brought back to life at a time and used as his ability. For example, Rimbaud dug the previous Port Mafia boss and humanized him back to life to turn him as his ability. Despite being an "ability" thereafter, the resurrected person is a physical being and thus cannot be nullified. Furthermore, he once attempted to take Chūya Nakahara as his ability, where Rimbaud hinted that his injuries would later regenerate and be healed once he becomes Rimbaud's ability.
Because it does not adhere to the laws of physics, Illuminations proves to be a natural weakness against Chūya's Upon the Tainted Sorrow, which is heavily anchored on the laws of gravity to function fundamentally. For instance, when Chūya had been enclosed in Rimbaud's hyperspace, the latter produced high-density atmosphere and spatial waves that defy the laws of physics. Since the spatial waves were also massless, Chūya's ability was almost ineffective, as the waves could not be readily countered with gravity. Furthermore, since Illuminations allows Rimbaud to manipulate everything in his hyperspace, it is also capable of levitating himself and the contents inside the space. Nevertheless, like all other abilities, one of the ways to deactivate the ability is through No Longer Human, though Dazai must specifically have a direct contact with Rimbaud through whatever connecting medium to effectively nullify his ability and, in extension, his hyperspace.
- In the light novel, Rimbaud's hyperspaces are described to be crimson in color, while the anime depicts them as having a yellowish hue.