It's in the
community update! Let me find the link.
EDIT
Here you go, It says:
Unlike Baldur’s Gate 3’s other playable protagonists, the Dark Urge is a fully customisable character. Should you prefer that this darkness take the shape of a doe-eyed gnome instead, or think true evil is a half-orc armed with a bongo, the choice is yours: from your class and species, to your gender and overall appearance, and even your name.