Great Black Sword/Underworld Icicle (大黒刀黄泉氷柱, Daikokuto/Yomi Tsurara) is part of huke's creations and is presumably part of the Black★Rock Shooter character roster. She only appears in huke's PIC5 artbook.
Great Black Sword/Underworld Icicle is a girl with shoulder-length black hair and red-orange eyes. She wears a long, black sweatshirt with white stripes on the arms and a wide neck. She also wears black thigh-high stockings, a black scarf, and black armored boots. On her left shoulder is what appears to be a large mechanical sword.
Her weapons are a katana, carried on her right shoulder, and in her left hand, there seems to be a black sword of enormous length which is most likely what she got her name from.
- Since her name is also referred to be Underworld Icicle, there might be a connection to the character Underworld Vulcan.