>>2063580
Probably a Tsuchigumo
>Tsuchigumo are traditionally giant spider monsters, though unlike Jorogumo they're rarely depicted as beautiful women
>Appears in a story where the hero receives divine aid from Amaterasu to defeat one with a legendary weapon (though a sword and not a spear in this case), mirroring the apparent plot
>Battle takes place in a cave and Tsuchigumo are "those who hide underground"
>Name is also used to describe clans who were antagonistic to early Japanese rulers
Jorogumo is also possible given that they're women/spider demons with fire powers and she has a lantern there
But I wouldn't be surprised if she was the main villain and a Tsuchigomi rising up against the Japanese with other mythical beings like the Mishiguji who fell out of favour