Rider Alter is Saber Alter in very specific swimsuits (and should really be merged into saber alter because using a different character tag when Kiyohime or Salter wear swimsuits completely contradicts how we've handled it for any other character), not Artoria Pendragon Alter as the name would imply and Saber Alter is a corrupted version of Saber, Artoria Pendragon is a tag for an entirely different "branch" of her convoluted character tags. The correct tag is currently Artoria Pendragon Rider Alter and would have been Saber Alter if they cleaned up the mess around her character tags.