I couldn't finish 'em. Looks like this's gonna get complicated.
Arachne is an enemy in Final Fantasy Dimensions. It is encountered in the Challenge Dungeon of the The Dragoon. Since the Challenge Dungeons do not appear outside the original phone release, it is only dummied in the other mobile versions and therefore not available in any English version of the game.
Arachne is the name of a mythological Greek weaver who boasted she had skills surpassing that of Athena, the goddess of weaving. For this hubris, Athena transformed her and her descendants into spiders.