Nyx

If given Nectar, Nyx will give you the Black Shawl.

After giving Nyx 6 Nectar, she cannot be given any more gifts until you complete a favor for her.

Once you have completed the favor, she can be gifted Ambrosia, although she does not give a Companion in return.

Nyx's affinity gauge is maxed out at 9 hearts, requiring the gifting of 6 Nectar and 3 Ambrosia total.

Favor

Nyx's favor is part of the Fated List of Minor Prophecies and requires you to reunite her with Chaos. At some point, she will tell you that she has sensed Chaos' attempts to communicate with her. She will later inform you that the bridge to Chaos cannot currently be accessed through the eldest sigil in the administrative chamber, but you can change this using a certain amount of Darkness. An upgrade will become available at the House Contractor, requiring 3142 . The reason for the precise value is not known, but it is the constant pi rounded to four digits times one thousand, and also the total number of greek gods according to the Theoi Project. Previously, the value was 8888 . Once purchased, Nyx will then use the eldest sigil to visit Chaos' realm, and you can even encounter her there in your run. When she returns to the House of Hades, her affinity gauge will no longer be locked, and you can give her Ambrosia.

'...Mother Night, we like to call her, though rare is the occasion when she dotes on us. She has her many, many children to look after, many of whom reside now in locales beyond my reckoning, and perhaps beyond hers. Yet, nonetheless, she toils about the Master's House, and conducts such affairs that fail to reach his notice or gain his attention. She and the Master do enjoy a sort of harmony, for even as he tends personally to the dead, she watches over the domain itself. They tolerate each other, in respect of one another's power.'

Unlocking the complete Codex Entry requires deepening Zagreus' relationship with Nyx.

'She could have made the Master's life eternally more difficult, down here, if she so chose. Had every right to, perhaps, when her own daughters, the Fates, determined that the Master ought to govern where once she alone presided. But, Mother Night does not possess a mortal's pridefulness; and her commitment to the Underworld and her children is absolute.'

For quotes and dialogue regarding Nyx, please refer to Nyx/Quotes.

Chaos: Nyx is regretful about being so estranged from her own parent, as they have not talked to each other since the beginning of creation. This was due the expectations Chaos had laid onto Nyx, and due to Nyx's being occupied with her work and forging her own path. Zagreus may choose help her reunite with Chaos, and the two will be able to rekindle their relationship.

Thanatos: Nyx seems to have a positive relationship with her son. He offers to help with matters in the House, but she instead encourages him to continue helping in his own way.

Hypnos: Believing that Hypnos is too dependent upon her, Nyx endeavors to foster independence in her son by maintaining distance in their relationship; she instructs him not only to refrain from calling her 'Mom' in the Great Hall, which he is want to do, and asks him not to engage her in conversation in work hours. She presumes or anticipates to some extent that others will find Hypnos' disposition dislikable, as she will, without prompting, offer to chastise Hypnos on others' behalf. Moreover, it is apparent that Nyx rarely imparts praises upon Hypnos: when she does tell him his "efforts are to be commended" for the first time, Hypnos assumes she means someone else commended him and makes several guesses as to whom—going so far as to guess Hades without Nyx once occurring to him as a possibility. Nevertheless, Nyx's attempts to encourage Hypnos' independence appear to stem from maternal care just as much as they may stem from her continued concerns over Hypnos' work ethic; she is expressly reassured to see Hypnos proving himself capable, and what boundaries she sets for him are ones she believes to be in his best interests, regardless of his opinion.

Zagreus: Nyx cares for Zagreus as if he is her own child. She fully supports his decision to leave the Underworld and helps him by giving him the Mirror of Night and contacting the Olympians on his behalf. She comforts him when he fails, but never sugarcoats the difficulties ahead. It is revealed that Nyx asked the Fates to revive the stillborn Zagreus despite it being against the rules.

Hades: Hades and Nyx manage the domain together. They mostly tolerate and begrudgingly respect each other, even if they fight at times. While he controls the punishment of Titans and primordial gods, she appears to have some kind of arrangement with him to have avoided a similar fate for herself.

Persephone: Persephone and Nyx shared a friendly relationship during Persephone's time as Queen of the Underworld prior to Zagreus' birth. Nyx describes Persephone as respectable and stately, while Persephone was grateful for Nyx's company and support during her initial time in the Underworld, later stating that she missed her and Cerberus the most out of all the denizens of the Underworld. Upon Persephone's return to the Underworld, the two of them continue to be on good terms, with Persephone being grateful for Nyx's role as Zagreus' foster mother in her absence and Nyx's part in engineering her reuniting with him.

Megaera: Nyx acts as Megaera's advisor and direct employer. She consoles Megaera and reminds her of their duties to the House.

Dusa: Nyx disapproves of Dusa for her tendency to overwork herself and associating with Zagreus. She eventually removes Dusa from her job without warning. It is when Zagreus intervenes that Nyx is persuaded to allow Dusa to work in the House again, although not without "certain stipulations".

Olympian gods: The Olympians look down on Chthonic gods as a whole.

• Athena seems to be on good terms with Nyx, whom she considers to be shrewd. She is one of the first Olympians to respond to Nyx's plea to help Zagreus. At one point, she confesses that she sometimes envies Zagreus' relationship with his (foster) mother, having never had one herself.
• Ares mentions that Nyx is ill-liked upon Olympus, though he has always longed to meet her, partly due to a sense of gratitude in her role in his own work. After enough interactions with the both of them, he will reach out to form a correspondence with her.
• Zeus seemed to believe that Nyx is the closest thing Hades has to a Queen.

• Nyx holds a managerial role in the House, leaving bureaucracy and ruler-ship to Hades and Persephone.

For additional information on Nyx that does not pertain to Hades, see Wikipedia's article: Nyx