|Armor of Fafnir|
|Title:||Blood Armor of the Evil Dragon|
|Transliteration:||Akuryū no Chiyoroi|
|Owner:||Saber of Black|
|Maximum number of targets:||1 person|
Armor of Fafnir: Blood Armor of the Evil Dragon (悪竜の血鎧, Akuryū no Chiyoroi?) is an ability that embodies and re-enacts the legend of Siegfried bathing in dragon-blood from Fafnir, granting him a dragon's body with invulnerability that made all weapons ineffective against him during his life.
Despite its name, the Noble Phantasm itself is not the armour itself, but rather Siegfried's very skin. That skin was composed of dragon scales that wouldn’t be wounded by any blade or any spell and the skin was tougher than steel. Saber of Red commented on how she was able to slice through his gauntlet, but what stopped her blade was actually the flesh that was underneath it. Even a Servant's armor shouldn't be strong enough to remain uncut after receiving her slash. It is noted that his dragon blood armour actually surpasses Kavacha and Kundala in raw sturdiness.
His skin is able to cancel physical attacks and magic equivalent to B-rank or lower, allowing him to take hits to vital areas without worry. It requires attacks of A-rank and above to harm him, but they register as damage only after the defensive values of an amount equal to B-rank are subtracted from them. When facing Noble Phantasms wielded by proper heroes, it gains defensive values equivalent to B+ rank. It caused him to lose the joy of battle because it did not allow him to feel the sensation of struggling against death, his body proofed against any and all attacks making it possible to slaughter enemies without much thought like simple labor.
Even without an A-rank attack, it is possible to pierce it under special circumstances. Lancer of Red's spear possesses power proportionate to an A-rank attack even without activating it as a Noble Phantasm, and while that would not be enough on its own to land a blow, Lancer's immense physical strength and transcendent technique allow for a destructive force great enough to cause harm. The wounds he inflicts are shallow due to the circumstances, and even though they number over seventy on vital points like arteries and his forehead, healing magecraft from his Master restores Siegfried to normal immediately due to their minor damage.
Due to a linden leaf sticking to him during the bathing process, he has a leaf-shaped mark upon his back that marks his only weakness. His back does not gain defensive values, and he is unable to conceal it. Due to his fame, it will become the primary target should his identity be found out by others, causing Gordes, his Master, to act with as much caution as possible to avoid revealing his identity.