The costume set was uncovered by Akko and company as they were trying to find a way to break the time loop. As the set is seemingly ordinary, neither Akko nor her friends were privy to its significance.
It is later revealed that the set belonged to Molly McIntyre and was used to contain 6 of overall fragments of her Ghost Witch half while the seventh one in Time Void behind the Chamber's Sealed Door by the faculty of Luna Nova Magical Academy — by bringing the complete set back to Luna Nova, the gang have unknowingly allowed those fragments to return to Molly's human half and allowed her to remember who she was before seeking the seventh and final fragment to become whole again.
The Classic Witch's Robe is a purple tattered robe that has a necklace with five stones. When one looked closely, the stone has a symbol in form of 8-pointed star. Found among the loots at Ant Queen's lair in Shaula Desert.
Classic Witch's Belt
A tattered witch's belt that has long outlived its useful life.