Hear me, Adagium! On my honor as king, I will vanquish you!
Regis
Regis Lucis Caelum is a boss in Final Fantasy XV: Episode Ardyn fought at the Citadel at the end of the third chapter. He wields the power of kings opposed by the player as Ardyn Izunia, wielding powers over darkness. The player can roam about the city of Insomnia as Ardyn before the battle to their heart's content to build Ardyn up with his "Descension" ability tree.
The battle draws parallel to the final boss battle of Final Fantasy XV, taking place on the same arena, and it starts to rain toward the end.
Battle[]
I swore to protect my people...
Regis
The player can fight on both levels of the arena.
Regis uses various techniques allotted to his bloodline. He begins the battle by just using the Sword of the Father, swiftly landing punishing combos. He has a substantial amount of health and can warp to maneuver around the battlefield and Ardyn's attacks. He warp-strikes as a surprise attack that knocks the player down. He casts powerful streams of lightning that he can home, and empowers his sword with electricity to strike it down to the ground to unleash frying sparks that travel across the ground to hit the player. He can also cast a spell where he generates slashes of light. Whenever charging his magical attacks, Regis can take damage, but he can't be interrupted. He can jump into the air to land upon the player, dragoon-style, scattering electricity about. Regis telegraphs his lightning magic by conjuring electricity in either his hands or sword, and he charges up fiercely enough to create distortions in the air.
After losing ~30% of his health, Regis summons Armiger and his weapons start to circle him. He uses Armiger with various techniques, such as sending his arms to attack in a single direction, raining them down from above, consolidating them into striking Ardyn all at once, or scattering them, having the weapons surround the player before commanding them to attack. He also wields a defensive formation that if not broken, results in Regis scattering the weapons and having them impale Ardyn.
If Regis and Ardyn lock blades, a button-mashing QTE activates; winning breaks Regis's formation and staggers him. When vulnerable, Regis kneels and does not retaliate for a time.
Regis casts Protect when on the last of his health to erect a magical barrier, and can attack while it's guarding him. The Protect spell has its own health gauge, which the player must deplete to get to Regis. Destroying the Protect puts Regis to vulnerable state. After his Protect is destroyed, Regis soon puts up his last stand and grows even stronger and gains an attack similar to the Armiger Storm used with Armiger Unleashed: his weapons circle around his back before he sends them flying while also slashing with the Sword of the Father to create a pillar of holy energy. This potentially puts Ardyn at 0 HP and thus activates his empowered state. Although Ardyn greatly powers up in this state, Regis may reduce Ardyn's max HP to zero, resulting in a Game Over.
Strategy[]
Though flashy, the battle isn't hard, and it isn't necessary to max out Ardyn's abilities before facing Regis to easily win. The battle starts with Regis only wielding the Sword of the Father, and the player only using the Rakshasa Blade. The player can evade Regis's assault with defensive maneuvers and use Daemonification when available, as although it can't finish off Regis (as he is a boss), it still deals remarkable damage. The player can keep a relentless offense with the Royal Arms command to impale Regis with all of Ardyn's arms, and then finish the combo to knock Regis down and put him to vulnerable state.
The player can summon Ifrit after the tech gauge charges. This also gives the Burned status to Regis, making him slowly lose HP over time.
When Ardyn falls to 0 HP at Regis's final offense, the player should go all out and attack non-stop until Regis falls.
Behind the scenes[]
Regis's Armiger appears based on its appearance from Kingsglaive: Final Fantasy XV; he wields a unique array of weapons rather than the royal arms, and his weapons are not transparent or glow blue. The maneuver where Regis block's Ardyn's Rakshasa Blade with all of his weapons at once was also used by him in Kingsglaive. Regis uses lightning magic prominently in both the movie and his battle with Ardyn in Episode Ardyn and uses some of the same animations Noctis uses in the main game. Regis kneeling when vulnerable is Noctis's 0 HP stance. Regis wields the Sword of the Father with a finisher that Noctis uses it in the main game at the end of a combo that grants him a temporary stat boost. Some maneuvers Regis performs in the final phase resemble the Armiger Unleashed.
Musical theme[]
Regis's boss battle has unique music that uses motifs from the Final Fantasy XV ending theme, "Somnus Ultima".