Nigredo is an NPC of the Great Tomb of Nazarick. She is the older sister of Albedo and Spinel. Nigredo is currently imprisoned in the "Frozen Prison," situated on the fifth floor of Nazarick.

Nigredo has an appearance similar to Albedo's, but her face doesn't have any skin. Moreover, her eyes and teeth are beautiful, but she has no lips or eyelids. As such, her appearance horrified all the guild members of Ainz Ooal Gown, who immediately attacked upon seeing her.

Though she acts insane and attacks her visitors without mercy if a baby-doll isn't given to her (because of her child, Victim, has been taken from her), Nigredo is guessed to be tender-hearted under normal conditions. She and Festonear opposed killing innocent people kidnapped from Re-Estize.

She is a Magic Caster whose power focuses mainly on information gathering. She is called one of the NPCs whose power is close to the highest level in Nazarick.

In the web novel version, she does not exist.

(Source: Overlord Wikia)