Half of them are obtained just by playing through the story, but the rest are optional. I’m going to go over where to find each Royal Arm, and the stats so you can decide which you want to use.

This guide will go over everything about Royal Arms in Final Fantasy 15 including:

Royal Arms Info - Brief info on Royal Arms and what they do. Royal Arms Locations - Where to find all 13 Royal Arms. Royal Arms Stats - The stats of each Royal Arm.

Royal Arms Info

The Royal Arms are weapons only Noctis can wield, and don’t always fill one of the other weapon types in the game. For example there are Bow and Throwing Star Royal Arms.

You lose HP each time you attack with a Royal Arm, but it is a small amount. You will want to keep an eye on it though because you could end up killing yourself if used at low health.

Each one also gives certain benefits, such as increased resistances or high attack power. They could also give other drawbacks such as slow speed, or reduced resistances. 

Royal Arms Locations and Stats

Sword of the Wise

First one when you first meet with Cor.

Stats

Attack: 194 +100 HP +30 Vitality +30 Magic +30 Spirit

Deals extra damage with preemptive warp-strikes.

Axe of the Conqueror - Tomb of the Conqueror

Required right after getting the Sword of the Wise. 

Stats

Attack: 483 +60 Strength -80 Vitality

Very high damage, but slow and lowers defense.

Swords of the Wanderer - Waterfall Cave Dungeon

This dungeon is required as you go through the story.

Stats

Attack: 153 +50 Vitality +50 Spirit

Attacks with multiple swords.

Blade of the Mystic - Right before Titan Trial

Stats

Attack: 396 +150 HP +30 Vitality +20% Dark Resistance

Scepter of the Pious - Malmalam Thicket

This is an optional dungeon near Old Lestallum.

If you are going through the story, your party will ask you if you want to stop there while you are on a drive. You will be able to go back at anytime. 

Stats

Attack: 237 +150 Magic +50% Dark Resistance 

Katana of the Warrior - Mine after the Leviathan Trial

Stats

Attack: 361 +100 Spirit +25% Fire Resistance +25% Ice Resistance +25% Lightning Resistance +50% Dark Resistance

Trident of the Oracle - Given to you by Shiva during the story

Stats

Attack: 388 +60 MP +30 Vitality +30 Magic +30 Spirit

Makes illusions with each attack.

Sword of the Father - Get automatically during Chapter 13

Stats

Attack: 141 +100 Strength +100 Magic

Star of the Rogue - Myrlwood

This is southwest of Vesper Pool. Vesper Pool is to the northwest of your map. A level 38 Treant blocks the path to the tomb

Stats

Attack: 177 +20% Fire Resistance +20% Ice Resistance +20% Lightning Resistance

Weapon is thrown in arcs to the left and right.

Mace of the Fierce - The Rock of Ravatogh

This is a dungeon to the far west on the map.

Stats

Attack: 334 +300 HP -50% Ballistic Resistance

Bow of the Clever - Balouve Mines

This is a dungeon in Liede, the starting area, but you won’t be able to get it at the beginning. There are high level enemies ending with a level 52 boss. You can find this dungeon south of Hammerhead near the road to Galdin Quay.

Stats

Attack: 203 +80 Magic +50% Ballistic Resistance

Attack from range.

Greatsword of the Tall - Costlemark Tower

This is a dungeon that’s southeast of Cauthess in the Fallgrove. You can only enter this dungeon at night. A level 58 boss blocks it.

Stats

Attack: 518 +200 HP -30 Spirit -40% All Elemental Resistances

Shield of the Just - Thommels Glade

This is an area that’s west of Cauthess. There is no dungeon or anything.

Stats

Attack: 251 +1,000 HP -50 MP -100 Strength +200 Vitality +10% to all Resistances 

That’s all of the Royal Arms in Final Fantasy 15. Now you can try them all out for yourself to see which you like the best. Let me know if you have any questions!