|“||No, that's not it. What I want...is you.||”|
—Volume 015 , Chapter 083
Nephero Styx Lethe ( ネフェロ・ステュクス ・レテ , Nefero Sute~yukusu Rete ) is the monarch of the Grand Sky Duchy , a vassal state of the Sun Kingdom. He is also known as the "Crimson-Haired Grand Duke" ( レッド ・ヘア・グラン ・公爵 , Reddo Hea Guran Kōshaku ) .
Nephero’s most striking feature is his dark crimson hair which has earned a place in his epithet. He wears a single tube-style weave earring.
From his current appearances, Nephero seems to have a self-indulgent, childish character, showing when he becomes excited at being chased by Livius for kidnapping Nike.
He also seems to find attached and taken women more alluring than single women. He is noted to be "creepy," by more than one of his subordinates.
Nephero can also be observant, ambitious and unafraid at taking risks to achieve his goals, even going as far as to nearly sexually assaulting Nike to break her will and keep her from returning to Livius.
The Sky kingdom presides over the Elmarela lake which feeds the two great rivers that supply the whole Continent's main water source. During Leonidas III reign he desired control over the Elmarela and accused Nephero's grandfather of treason. This resulted in his death as well as a culling of Lethe family.
Nephero who was just a boy at the time rode all the way to the Sun capital and confronted the King, threatening to destroy the Elmarela but Leonidas merely found it amusing.
Later in his life an intense winter plagued the Sky Duchy causing food shortages and a large proportion of the population died. It was during this time Nephero's father died and his older brother Catra fell ill leading him to ascend to the throne. At this point the Sky Duchy was a vassal state of the Sun Kingdom and aid was requested but denied, this further fuelled Nephero's hatred.
Under his leadership the Kingdom was restored. A lucrative salt production was created where it was sold in the black market for 5x the usual price. Some of the proceeds were used to fund the Rebel fraction which Nephero supports. This caused a rift with Catra, who was suspicious of the faction and opposed Nephero’s involvement in it. As a result, the brothers grew estranged.
Seeking further vengeance against the Sun Kingdom Nephero kidnaps Nike to be used as a weapon against Livius. Having heard tales of her powers, he desires her to be used as a weapon and to keep her all to himself. Even when Nike rejects him since she is already engaged to Livius, Nephero forces her to consume medicine that prevents her from using her powers against him and seriously injured Galta in order to make Nike his hostage. When the Dutchy is nearly devastated by a collapsed waterway from an earthquake, Nike helps the people, which endears her to Nephero. He tries to force her to marry him but she refuses. He takes Sheila’s ring from her and order hasty preparations for the forced marriage. When he finds her snooping in his room to get the ring back, he attempts to rape her but when she begins to cry, he decides not to go through with it, as he can’t stand tears.
Altaria ‘helps’ Nike escape, which angers Nephero and he organizes a search party to find her. Once they are found, however, Altaria reveals he deceived both Nephero and Nike; he manipulates Nike into unleashing catastrophic storms across the region, and the blame would fall on Nephero, as he has kidnapped her. Nephero attempts to stop Nike but is unable to. Once she finally comes to her senses, Nephero attempts to apologize to her and Livius but they don’t have time to listen when debris is about to fall on them. He saves them and is left blind and without usage of his limbs. Although Nike hates him and can never forgive him, she feels pity for him. In order to rebuild relations with the Grand Sky Dutchy, she keeps the assault a secret and Livius is lenient in Nephero’s punishment for the kidnapping, as being blind and paralyzed for life is punishment enough.
Nephero and Catra reconcile once they realize Altaria’s deception, and work together to rebuild the country.
"Become a decoration that exists only for me"
Nephero has a complicated relationship with Nike. He sees her as an object - "weapon", and kidnaps her. He threatens to kill/beat Galta, Nike's body guard if she does not co-operate. He forcibly kisses her in order to transfer a medicine which suppresses her wind magic. He has expressed an interest in taming her and using her for entertainment.
Nike in return resoundingly resents Nephero; however she does not resent the people of the Sky Duchy who have endured hardship. She helps them even at the cost of her own wellbeing, it is this aspect as well as her own resilience against his advances that causes him to want to claim her as his own wife. He attempts to rape her as a way to fully claim her (as her engagement to Livius was not yet consummated) but he backed off once she started crying.
He ends up feeling remorse for his actions towards Nike when Altaria manipulates her into using powerful storms to destroy the country. He risks his life to try and stop her, and ends up being blind and paralyzed. Although Nike still despises him, she chooses to keep the assault a secret from Livius in order to build peaceful relations between the two kingdoms.