Image search led to a seven-year-old Reddit thread here: https://www.reddit.com/r/grandorder/comments/4shjz2/sc%C3%A1thachs_new_armor_i_love_it_x3/ in response to a now-deleted twitter post by maple_luwen, which appears to have been the original source. According to a Redditor who had read their Twitter, despite the resemblance this isn't Scathach and isn't affiliated with FGO or Type/Moon.

Also, the original tweet had precisely half these dimensions, so this is probably a waifu2x upscale.

Arcana55 said:

Image search led to a seven-year-old Reddit thread here: https://www.reddit.com/r/grandorder/comments/4shjz2/sc%C3%A1thachs_new_armor_i_love_it_x3/ in response to a now-deleted twitter post by maple_luwen, which appears to have been the original source. According to a Redditor who had read their Twitter, despite the resemblance this isn't Scathach and isn't affiliated with FGO or Type/Moon.

Also, the original tweet had precisely half these dimensions, so this is probably a waifu2x upscale.

Appreciate the detective work!