In-Birth

The False Born, In-Birth（偽誕者(インヴァース)）are individuals who control the supernatural powers of EXS. In-Births are people who are neither alive nor dead - they are people without a birth.

Information

During a Hollow Night, if a person gets bitten by a Void, it consumes the person's soul and infects their body with the Void's common ability to manipulate EXS. If a person can maintain their sanity during all this, they'll be fully awakened as an In-Birth.

In-Births have access to the Void's common ability, the power of Manifestation (顕現化), which allows an In-Birth to give EXS some sort of unique shape; this is what's usually referred to as an EXS ability. In-Births through EXS also obtain enhanced physical abilities, which may be in order for their bodies to handle their given powers.

The EXS abilities are proportional to the wound the person received from the Void - the bigger the wound, the stronger the powers. Although, a bigger wound increases the chances of turning into a Void.

Official explanation picture from FRENCH-BREAD Twitch broadcast

If an In-Birth doesn't use their powers at all for several years, the powers of EXS and Void will eventually vanish from the body, making it relatively close to a regular human body. Once the powers have vanished, it is impossible to regain them anymore.

Vessel

The body of an In-Birth is called a Vessel (器(「ヴェゼル」)). It functions actually pretty similarly to a normal human body. A Vessel is used to store the EXS that an In-Birth needs to fight. When an In-Birth's Vessel is pierced, they are briefly immobilized and are unable to use their abilities for awhile.

Vessel is much more durable than a regular human body. The basic strength of the Vessel is also higher than that of a regular human body. The EFG warns all of its members to be careful not to use their full potential as it would appear as a sudden increase in physical exams and such.

Zero Vessel

Vessel Break, the Zero Vessel (器割れ(「ゼロヴェセル」)) is a state that an In-Birth might find themselves in. Strix is currently suffering from this condition.

In this condition, an In-Birth's abilities are restricted. They can barely even sense the EXS in their surroundings. Those in a Zero Vessel state become incapable of interfering with the flow of EXS, which means they cannot store EXS within their Vessel. This also means that they also can't use their powers.

It's hasn't been fully detailed how this condition can be cured.