After a dragon has evolved into a Maestro, they gain the ability to create a magical suit of armor in the Dragon Workshop, for their master to equip instantly during a battle. It is a labor of love, and represents the dragon giving everything about themselves to their rider. Arks are also capable of evolving into more powerful forms. As part of the armor set, the rider gains an Ark Weapon.
An Ark set has more properties that depends on the dragonar's capabilities, as they are crafted through random customization. Done as a made-to-order set, each part is best-fitted to match its wearer's preferences or others endangers the wearer's life. Most Arks in the present time of the series, are crafted from past Ark sketches stored within the Dragweiss for generations.
When Necromancia attacked Ansullivan, Eco who was captured made an incomplete makeshift ark for Ash. She made various copies adapted for Ash's immediate use until she made an original one during the battle against Mordred.