Cave Nilga

"I am the First Prince of The Spiral King Lordgenome: Cave Nilga! That's right... I am your brother!"

- Cave Nilga

Cave Nilga (ケーブ・ニルガ") is a character exclusive to the Nintendo DS video game, Tengen Toppa Gurren Lagann. Introduced as the First Prince of The Spiral King and older brother of Nia Teppelin, it is later revealed that he was a Beastman with fake memories implanted by The Spiral King as a mere experiment and disposable puppet, much like Nia herself before him.

Appearance
Initially, Cave appears as a fair-skinned human with sharp, angular facial features, such as his eyes, nose, chin and pointed ears. His overall appearance, specifically his hair and clothing, greatly resemble that of Nia's, with his short hair displaying hues of green and yellow with a light blue tint, and his clothes displaying various golden ornaments, jewelry and a cape. He also wears a very small pair of round glasses. He exudes an air of nobility and superiority.

After his Beastman nature is revealed, he assumes a much wilder visage, demonstrating his insanity. He loses his glasses, his eyes open wider with the scleras turning blue, and his hair assumes a flame-like aspect, gaining hues of purple and pink and resembling Lordgenome's flame-like Spiral aura.

Personality
Being the only human close to The Spiral King, having influence and royal power to rival the Four Supreme Generals, Cave is a vain, self-indulgent and truculent individual. He mocks Nia for being cast aside by their father and treats his comrades and underlings harshly, with no respect or consideration for their well being. Although he normally displays a cool and collected, albeit arrogant demeanor, he demonstrates elation and excitement at the prospect of bringing down people, enemies and comrades alike. However, he is shown to panic when things do not go his way. When he finds out he is actually a Beastman, he goes mad with incredulity and rage, and turns even more violent, fixated on destroying Gurren Lagann and Team Dai-Gurren.

History
Note: The events described below peratin only to the Nintendo DS game and are non-canonical to the plot of the anime.

After Dai-Gunzan is stolen by Team Dai-Gurren, Cave is called into a meeting with Lordgenome and the remaining three Supreme Generals. He is ordered by the Spiral King to take the flagship Dai-Gunku along with a number of troops to attack the human rebel group.

Piloting Enkial, Cave boards the Dai-Gunzan, now Dai-Gurren. There, Tetori and Ziggitalis are piloting Zagaheadz in a fight against Gurren Lagann. Cave orders Ziggitalis to execute a suicide attack against Gurren Lagann, an order that causes even the members of Team Dai-Gurren to feel disgusted at how the First Prince treats his comrades. The beastman complies; however, instead of attacking Gurren Lagann, Ziggitalis detaches Tetori's Megaheadz from his Zaolegg and charges alone against Cave's Enkial, dying in the explosion. Taken aback and with his Gunmen damaged, Cave retreats.

Some time later, Cave again infiltrates Dai-Gurren, undetected, with the aid of Enkial's radar stealth capabilities. There, to his surprise and amusement, he meets Nia. He proceeds to introduce himself as the First Prince and her brother, telling her, to her dismay, about how the Spiral King has cast her aside, amused by the fact that she seems to be the only one oblivious to that fact. He then launches an attack intended to destroy the Dai-Gurren's food supplies, but the attack is foiled by Gurren, piloted by Rossiu. Before retreating, Cave uses Dai-Gunku's artillery to launch an attack against Dai-Gurren. This causes Nia to fall down a crevice, prompting Simon to go after her aboard Lagann.

After Adiane's downfall at the hands of Gurren Lagann, Cave once again intercepts Team Dai-Gurren aboard his Dai-Gunku. He once again mocks Nia, who replies stating that, if she is a manufactured princess, then Cave, too, is a manufactured prince; a statement that seems to get under his skin. He continues the attack, but is once again is driven away by Gurren Lagann, piloted by Simon and Yoko.

With Dai-Gunku's levisphere damaged in the previous battle, the battleship has its flight capabilities hindered. Cave orders his troops to land the ship in a way as not to be seen by Team Dai-Gurren. When the Dai-Gurren approaches, Cave commands an attack from the sky with the use of flying Gunmen, which is yet again repelled by Gurren Lagann. As Cave grows increasingly agitated due to Team Dai-Gurren and Gurren Lagann's fierce resistance, Cytomander and Viral arrive to deliver a message from Lordgenome ordering him to stand down and return to Teppelin, all the while being mocked and berated for his failures by the duo, much to his indignation.

Upon his return to Teppelin, Cave tries to justify his failures to his father. However, The Spiral King responds by telling him that he is no father of his, nor is he Nia's brother. Instead, he reveals to Cave the truth: that the First Prince is nothing more than a Beastman made as a plaything for The Spiral King to be entertained by. He tells Cave to take a good look at his true Beastman form; a visage to which the former prince responds with madness and agony.

Driven by pure rage, Cave once again attacks Dai-Gurren aboard his Enkial and demands for Gurren Lagann to show up, claiming that he would devour it. Simon and Rossiu promptly respond to the attack, boarding Gurren Lagann and engaging in battle against Cave and his Enkial. Finally, the two boys manage to defeat and destroy Enkial. In a final bellow of rage, the Beastman refuses to relinquish his title as a prince, and finally perishes in the explosion. Nia reflects upon the events that have just transpired. Demonstrating sorrow for the Beastman's fate and bidding farewell to her false brother, she is more determined than ever to put a stop to her father's misdeeds.