Pencils, ink, aquarelle, and Oxford commas.

General CH ttrpg entity design & illustration:

A Void Child (sometimes "Void Angel") is the result of extended suffering through voluntary martyrdom (originally by the Nameless King in order to gain insight into the nature of the Void).

In the final phase of being martyred, after the physical removal of the face, a powerful Word of Alteration erases their existence, leaving no knowledge or physical evidence throughout reality, and transferring their "essence" outside time and space, i.e. in the Void.

All that remains of the martyr is the experience of the inflicted suffering which can manifest (or project) into reality. As such they are believed to be (re)born in and of the void, hence the name "Void Child".