Natsu Dragneel vs. Leo (Eclipse)

Natsu Dragneel vs. Leo (Eclipse) is an anime-exclusive fight fought between Fairy Tail Mage Natsu Dragneel and Eclipse Celestial Spirit Leo.

Prologue
The enraged Eclipsed Celestial Spirits clash with the Mages at Astral Spirytus, due to the Mages interrupting Liberum. After that, the Spirits separate, retreating to each others' gates, leading them and the Mages who followed them to different areas. Natsu takes Leo's key and, together with Happy, follow Leo to an ancient ruins area, where the two clash together. The Eclipse Spirit aims for Natsu's Exceed Happy, battering him away, thus grounding his opponent. Suddenly, the ruins start shaking, giving the Dragon Slayer a motion sickness, in which Leo exploits and attacks his weakened enemy, just before a mysterious huge dark-green beam of energy appears, drifting them away.

After Natsu and Happy reunite with Wendy and Carla, the travel back to the ruins where Natsu picks up Loke's scent leading them into an altar room inside the ancient pyramid. After finding a secret passage, the team enter as Natsu stating that Loke will not escape. On their way, they meet Ophiuchus, who is revealed to be the controller over Astral Spirytus, she then starts torturing the Mages with her medical equipment. Later, Loke appears, informing Ophiuchus of the ceremony. The walls the shatter, revealing another area where Ophiuchus shows her true form and Loke readies for the perfect freedom.

Battle
Loke starts transferring the power to the zodiac constellations, as Natsu charges at the Eclipsed Spirit, dodging his attacks. The two then fisticuffs with their flames, as Natsu mocks his opponent's flames. He then tells Wendy and the Exceed to retrieve the Celestial Globe and blocks Leo form stopping them. The two then engage fiercely, as Leo explains the origin of his Magic Dark Regulus and calls Natsu to come at him, just for him to absorb the Dragon Slayer's flame. As he continues to ingest Natsu attacks, he assaults the latter with his Sanction of Darkness battering him against the wall. Natsu then appears hardly harmed and repays him with his Fire Dragon's Iron Fist. Natsu then taunts the spirit for not absorbing his attack, before the two clash yet again, with Leo stating that Natsu might give him some amusement.

As Wendy falls due to the Celestial Globe's shockwave, Natsu get distracted just to be hurt from Leo's projectile attacks. As Natsu breathes his Fire Dragon's Roar, Leo, surprisingly, fires his Roar of Darkness, dispelling Natsu's attack. Natsu clashes with Leo several times using his Crimson Lotus: Exploding Flame Blade, just to overpowered by the spirit's Exploding Flame Blade of Darkness, battering him again. Leo then taunts the exhausted Natsu, stating the darkness is dominating the light, before striking the latter once again with his Purge of Darkness. As Natsu is out of his energy, Eclipse Leo chants a prayer, just to be told to stop by the risen Natsu. As Leo questions his determination to deprive them from their freedom, Natsu replies that that will make Lucy cry. Leo then assaults Natsu with his darkness flames, but Natsu then stops him and starts eating his darkness, activating his Black Fire Dragon Mode and defeats him with his version of the Exploding Flame Blade of Darkness.

Aftermath
Natsu then force closes Leo's gate, hoping for the ritual to stop. Unluckily, Liberum continues, with Ophiuchus starts to chant a mysterious prayer. She then reveals that sending Leo back to the Celestial Spirit World alongside the other spirits was a prat of her plan to empower the Eclipsed Celestial Spirit King.