The Nemean Pelt

“A trifle. His armor is special, that’s all.”
“His... armor?” Tine asked, turning to look at the archer, who had returned to earth.
The archer was wearing almost nothing that could be called armor. The only things covering his upper body were the strange, patterned cloth draped over his head, and other patterned cloth wrapped around his arm.
“It is most likely the hide of some species of demonic or divine beast. It can have been no small task to work it into that form, but it was probably originally something like an Ugallu.”
Gilgamesh gave the name of a Babylonian monster as an example, but that was not enough to satisfy Tine.
“You mean that this hide repelled all of Your Majesty’s tremendous blows?” She pressed.
“Numbers do not enter into it. Divine or demonic beasts sometimes reject human civilization itself in that way. A moment ago, I hit him with anything and everything — not only my first-class armaments, but even the Noble Phantasms of lower orders that I would ordinarily not even bother firing. I do not believe he repelled them all with skill alone. If he did so with his body, or some form of magical energy, however, it would fail to explain the fact that the hide is completely unharmed.”
At that point, the King of Heroes narrowed his eyes, and tightened his grip on Merodach, the sword of selection.
“Occasionally a creature of that sort appears — a singularity that rejects human civilization itself. At the very least, no tool created by humans will pierce that skin.”

-F/sf Vol 3