Cave Nilga

In his human guise Cave projects aristocracy. Golden ornaments and jewelry decorate his clothing, a cape hangs from his shoulders, and a tiny pair of round spectacles rests on his nose. Sharpness defines his face; the eyes, nose, chin, and pointed ears all come to angles. His short hair blends green and yellow tones under a faint blue cast, and both the cut and the wardrobe echo Nia so strongly that the sibling deception sells itself.

The unmasking rewrites him. The glasses vanish, his eyes stretch wide as the scleras turn blue, and his hair flares upward into a flame-like shape streaked purple and pink, an image recalling the burning Spiral aura of Lordgenome himself.

Standing closer to the Spiral King than any human, with influence rivaling the Four Supreme Generals, Cave wears his privilege badly. Vanity and self-indulgence drive him. He taunts Nia over her abandonment by their father, and he spends the lives of subordinates without a flicker of concern. His usual manner is chilly, collected arrogance, but cruelty excites him; watching anyone brought low, ally or enemy alike, makes him giddy. Setbacks crack the mask quickly and leave him panicking. Learning what he really is destroys him entirely, tipping him into a raving obsession with wiping out Gurren Lagann and Team Dai-Gurren.

These events belong solely to the Nintendo DS game and sit outside anime canon. After Team Dai-Gurren steals the Dai-Gunzan, Lordgenome summons Cave alongside the surviving Supreme Generals and sends him after the rebels with the flagship Dai-Gunku. Boarding the captured fortress in his custom Gunmen Enkial, Cave commands the Beastman Ziggitalis to make a suicide run at Gurren Lagann. The order disgusts even the human onlookers, and Ziggitalis obeys it in his own way, hurling his machine into Enkial instead and dying in the blast. Shaken and damaged, Cave withdraws.

He later slips aboard the Dai-Gurren unseen behind Enkial's radar stealth and comes face to face with Nia. Delighted, he names himself her brother and the First Prince, then relishes telling her that their father has thrown her away. His strike on the ship's food stores fails when Rossiu intercepts in Gurren, and his parting artillery barrage from the Dai-Gunku knocks Nia into a crevice, sending Simon after her in Lagann. Following Adiane's death he attacks again, only for Nia to turn his own taunt around: a manufactured princess, she notes, must have a manufactured prince for a brother. The line visibly rattles him, and Simon and Yoko drive him off in Gurren Lagann. With the Dai-Gunku's levisphere crippled, he grounds the ship out of sight and launches an aerial ambush that fails like the rest. Cytomander and Viral then arrive bearing Lordgenome's recall order, mocking his failures all the way, to his fury.

At Teppelin the Spiral King cuts him loose. Cave is no son, no brother to Nia, merely a Beastman fitted with counterfeit memories for the King's amusement. The revelation shatters his mind. In a final frenzy he assaults the Dai-Gurren in Enkial, howling for Gurren Lagann to face him, and Simon and Rossiu destroy the machine. He dies in the explosion still refusing to surrender his stolen title. Nia grieves for the false brother all the same, and the episode steels her resolve to end her father's cruelty.