Regalia of Eochaid is a Straight Sword in Elden Ring. The Regalia of Eochaid scales primarily with Dexterity and Arcane and is a good Weapon for Arcane Builds. 

Elden Ring Regalia of Eochaid Notes & Tips

• Weapon Skill: Eochaid's Dancing Blade
• This weapon cannot be infused with Ashes of War
• Cannot be enchanted with Magic nor buffed by Consumables
• Regalia of Eochaid can be upgraded by using Somber Smithing Stones
• Sell Value:  

   500

• Eochaid's Dancing Blade's damage is based on total Attack Rating, so using things that boost your AR will increase its damage significantly.
• Winged Sword Insignia, Rotten Winged Sword Insignia, and Millicent's Prosthesis all boost the damage of this Skill since each strike of the corkscrew is considered an attack.
• Marais Executioner's Sword has the same Skill, but that Weapon does more damage with it since it has higher Attack Rating. If you like the Skill, but wish it did more damage, try using that weapon instead.
• Despite having C scaling in both Dexterity and Arcane, you get far more damage out of this Weapon for each point of Arcane. Past 20 Dexterity damage starts to decline with this Attribute, making this a great weapon to pair with Arcane spellcasters, since you typically invest heavily into this Attribute to maximize damage.
• Eochaid's Dancing Blade does predominantly Physical Damage, with some Magic Damage, but not a lot.
• Since it can be obtained early, it's a decent option for dex-arcane or just arcane builds against enemies that can't bleed/if you want to deal magic damage without investing in int. Don't give it more credit than it's due though, the magic damage is nice, and the WA is good in certain situations (blocking enemies and the likes), but the damage is, at best, decent.
• NOTE: As of Patch 1.08, Straight Swords poise damage has been reduced only on PVP.
• NOTE: As of Patch 1.09, the scaling values of this weapon were changed. Please refer to the Upgrades Table of this weapon below. Additionally, the running attack speed, first attack speed and speed of guard counter of straight sword has increased. The attack recovery time has also decreased.
• Known as Eochaid's Gemsword in 1.00 version of the game.
• Other notes and player tips go here

Regalia of Eochaid PvP Poise Damage in Elden Ring

Patch 1.10 adjusted PVP Poise Damage of all Weapons including some Spells and Incantations. Please take note that these adjustments are exclusive to PVP.