Rho Aias

Rho Aias: The Seven Rings that Cover the Fiery Heavens is the shield used by Aias, and the only shield capable of stopping the javelin of the great hero. It was a bronze shield covered in seven layers of oxhide, which the javelin, having never before been blocked during the Trojan War, pierced to the seventh layer before stopping. Its existence was sublimed into a Conceptual Weapon that is said to be an absolute defense against any thrown weapon. It takes the form of seven layered Bounded Field in the shape of an iridescent flower with seven petals in reference to the Hyacinth flower that bloomed from Aias' blood as he died. Each layer has the defensive power of a fortress wall, and Archer cannot personally recall any thrown lance that would be capable of penetrating even the first layer. It is necessary for its user to provide constant magical energy to form the shield, and if it is damaged, they will feel pain and receive damage in accordance.

Archer came into contact with it some point in his life, and added it to his library of weapons and defensive armaments stored in Unlimited Blade Works. He uses it as his main defense, as it is the one in which he has the most proficiency, and Shirou Emiya cites it as Archer's greatest protection. He uses it to defend against Lancer's Gáe Bolg, which manages to pierce up to the seventh layer before finally stopping. This action takes much of his energy, as it takes three times the amount of prana as a weapon in order to project it, and still leaves his arm and body damaged afterward. He can also project it from a distance, allowing him to shield Shirou from Gilgamesh's Enuma Elish without either of them realizing it. If it is used by Shirou after having access to Archer's knowledge, he is only capable of generating four petals in Heaven's Feel and Fate/hollow ataraxia. It is still powerful enough to help Bellerophon overpower Black Excalibur and temporarily deflect a charged shot of Hrunting. Shirou is able to project the full version during Unlimited Blade Works after "pulling it from the hill" of the Reality Marble in order to protect himself from Gilgamesh's onslaught of swords.