She's the 30th Queen of the empire, Her Highness Riana (also known as the Sword Princess); that Thor used to be from (first appearance in ch.6.1, pg.7)
Who went to use the magic sword that Thor secretly was trying to fix, but then his dumb ass of a father and butler done oof fucked up on it with the remaining repair that after Riana used it, magic sword went "I don't feel so good" and got destroyed (shattered af) during a battle cause it couldn't withstand her mana