Armiger

Armiger, known in pre-release material as Armiger Arsenal, and also known as the power of kings, is the means to wield the royal arms all at once. It is Noctis's Limit Break in Final Fantasy XV.

Mechanics
Armiger can be invoked during battle by pressing +  ( + ) when the Armiger bar is full. The player needs to collect three royal arms for it to become available. Using Armiger the first time earns the The Power of Kings achievement/trophy.

Armiger summons spectral weapons around Noctis to increase his speed and strength. In Final Fantasy XV Episode Duscae, it drains his MP and ends when it is fully depleted. The finalized game instead uses the Armiger bar, a separate gauge with no connection to MP.

Armiger turns all of Noctis's movements into warps. It enables him to take on any challenge alone, but it is intended to provide only a temporary increase in power since Final Fantasy XV stresses the importance of cooperation with one's allies. Before the Armiger bar depletes, can be activated by pressing  +  or  + —this allows the party to each take up a royal arm and attack as one. Killing enemies with Armiger Chain used to yield 100xp per kill, but this was raised to 3000xp per kill in patch 1.21.

The last stage of the Armiger Chain is:
 * First attack:
 * Sword of the Wise - Prompto
 * Axe of the Conqueror - Gladiolus
 * Sword of the Wanderer - Ignis
 * Blade of the Mystic - Noctis


 * Second attack:
 * Star of the Rogue - Prompto
 * Sword of the Tall - Gladio
 * Mace of the Fierce - Ignis
 * Bow of the Clever - Noctis


 * Third attack:
 * Scepter of the Pious - Prompto
 * Shield of the Just - Gladio
 * Katana of the Warrior - Ignis
 * Trident of the Oracle - Noctis


 * Final attack:
 * Sword of the Father - Noctis

In the second part of the Leviathan battle, Noctis wields every royal arm, including the ones he hasn't obtained yet. If a player can execute a complete combo, Noctis will finish using the same attack pattern he uses when finishing a combo with the Sword of the Father.

When using character swap and controlling someone other than Noctis, the AI-controlled Noctis will not initiate Armiger on his own.

Royal arms
Royal arms are used by Noctis. Using them as normal weapons drains Noctis's health when he attacks with them (when he is player controlled; AI-controlled Noctis with character swap loses no HP), but they are generally especially good against daemons. The royal arms are wielded at once during Armiger, during which Noctis doesn't lose health from wielding them.

Armiger Unleashed
Armiger Unleashed is a new battle style for Noctis from the Royal Edition, which lets him use weapons other than the royal arms in Armiger for various effects with unique movesets, although it also reuses some animations from other moves, like the blink-counter of the Holy spell from the Ring of the Lucii as well as a huge increase in how long the Armiger lasts. Armiger Unleashed is activated by having the Founder King's Sigil accessory equipped and pressing +  or  +  just like the original Armiger. It also has four new techniques for Noctis activated by holding or  as if you were activating an ally's technique. Timing your dodge will activate a Holy spell and performing a prompted block and countering afterwards will bring the Royal Arms in front of you and shoot them towards the enemy. The player can time their inputs to build combos, and it has been said Armiger Unleashed will be "difficult to get used to", and to be for "advanced players".

The Founder King's Sigil is found in northern Leide, near Keykatrich, by interacting with the statue of the Founder King after collecting all 13 Royal Arms.

One of the new poses as part of this technique was a signature pose Noctis was seen using against Stella Nox Fleuret in old Final Fantasy Versus XIII material, and was his "" for a time.

Story
Only those of Lucian royal blood can use Armiger, as only the members of this lineage are bequeathed the power of past kings. The ancient kings' power is enshrined in royal tombs scattered throughout the world and the weapons they house are special. Every new king's duty is to collaborate to the collective power of kings by adding their own royal arm to the mix, and princes embark on trips across the land to collect the arms of their forebears from their royal tombs. Many of the weapons have been lost, however, the location of their tombs unknown.

As depicted in Brotherhood Final Fantasy XV, young Noctis saw his father wield the power of the crystal weapons. He knows that he, as the heir to the throne, will be able to do so as well. Lucian kings wield the power of the Crystal, and through it gain various supernatural abilities, the ability to wield crystalline weapons that manifest out of thin air being one of them. It is a power passed to the new king by the souls of the former kings. The weapons of former kings are enshrined in royal tombs scattered throughout the world. The power of the royal arms, combined with the power of the Crystal, can destroy the Starscourge, which became known as the prophecy of the True King.

After Niflheim steals the Crystal and kills King Regis, Noctis sets out to reclaim his kingdom by collecting the royal arms of his forebears and to forge covenants with the Astral gods. He gains the power to use Armiger, and when Ravus Nox Fleuret confronts him at an imperial base, Noctis displays his power of kings to intimidate him, but Ravus is unfazed. During Noctis's battle against the Leviathan he enters a sustained mode of Armiger with the help of Oracle Lunafreya Nox Fleuret and the souls of the past kings. It almost expends all of his life force until Luna rushes to heal him.

As depicted in Final Fantasy XV: Episode Ignis, while Noctis is unconscious following his battle with Leviathan, his friend Ignis Scientia faces Ardyn Izunia, who unexpectedly shows off his ability to use Armiger. Ardyn reveals his identity as Noctis's ancient immortal ancestor whose soul has been corrupted by Starscourge, becoming the very embodiment of it. Ardyn fights Ignis with the power of kings, but Ignis survives by lending power from the Ring of the Lucii for a blood price.

Noctis eventually faces Ardyn at the Citadel to fulfill his destiny as the True King. The two duel both wielding the power of kings, but Noctis defeats Ardyn by striking him with each royal arm, delivering the final blow with the Sword of the Father. Noctis summons the spirits of the old kings to kill him so he can defeat Ardyn permanently in the afterlife. The royal arms appear around the throne, like they do when Noctis uses Armiger. He takes the arms to the realm beyond by having the spirits of the past kings plunge them into his body, and once the Caelum lineage is united in the afterlife, the combined powers of the kings and the Crystal erase Ardyn's soul.

Final Fantasy XV Episode Duscae
Several unique weapons must be collected before Noctis can use Armiger Arsenal. Each weapon the player collects unlocks a new ability to use with Armiger. The player can find Phantom Swords from the environment, and finding four maxes out the Armiger. In the final game, "Arsenal" was dropped from the ability name, and the weapons are not referred to as Phantom Swords. The Phantom Swords are unique to the demo.

Brotherhood Final Fantasy XV
In a flashback Noctis has of his childhood, King Regis drives away the Marilith daemon by summoning the royal arms to him at once. As an adult, Noctis faces off against the same daemon by using Armiger. Noctis wields Blood Edge and the Soul Saber when he uses Armiger, rather than his royal arms.

A King's Tale: Final Fantasy XV
Armiger can be used by Regis Lucis Caelum and even by Ardyn Izunia. The player progresses through a series of stages defeating monsters and daemons. The player can string combos together, juggle enemies in the air, and use magic. Regis can summon an ally whenever his combo count reaches 8, and he can use Armiger whenever it reaches 24. If he summons an ally before using Armiger, they will join the attack. If all three allies are summoned before Armiger, they will execute the powerful Bonds of Battle.

Final Fantasy Dimensions II
While not referred to by name, the Armiger Arsenal appears when a character performs the Phantom Sword ability taught from the Noctis Phantom Stone.

Dissidia Final Fantasy NT
Armiger automatically activates after Noctis's HP falls below a certain amount. While active, Noctis's royal arms will also attack when he performs bravery attacks.

Final Fantasy Airborne Brigade

 * Legend Cards

Final Fantasy Record Keeper
Armiger is Noctis's Overstrike Soul Break, learned from the Sword of the Father (XV). When invoked, Noctis dives diagonally toward a single target at high speed, and upon impact strikes the target with tremendous force that can break the damage cap. Noctis then enters Armiger Mode, gaining a bubble shield for 30% of his Max HP worth of damage, and raising his Attack a moderate amount while the shield is in play.

Final Fantasy Brave Exvius
Rather than summoning the same royal arms that appear in Final Fantasy XV, Noctis's Armiger shows the four "Phantom Swords" obtained in the Episode Duscae demo.

For Whom the Alchemist Exists
Noctis is an obtainable character during the Final Fantasy XV collaboration event. The is shown wielding seven royal arms in Armiger.

Development
In Final Fantasy Versus XIII, the weapons used in Armiger's execution were vastly different. Among them was a rod, a partisan, a lance, and firearms. Noctis's Engine Blade was also included. A man in a white robe (who became Ravus Nox Fleuret in the final game) and Stella Nox Fleuret also use powers similar to Noctis's.

Etymology
In the final game, the royal arms are named after the moniker of the king who wielded it, but in Episode Duscae the phantom swords had traditional names:

Galatine is synonymous with "Galatyn."

Trivia

 * The Astral Bahamut is associated with multiple swords. His summon attack is Ultima Sword that has massive glowing blades rain down on the enemy, somewhat similar to how the glowing weapons surround the wielder in Armiger. Lucian kings' ability to wield multiple weapons at once with Armiger could thus be a power originating from Bahamut, although not all of the royal arms are swords. Bahamut is the Astral of light, and the royal arms embody this element.
 * For April Fools 2017 Square Enix announced "Episode Kenny" where the player would play as Crow's Nest mascot Kenny Crow whose Armiger would be summoning crystalline fish.