A fortress designed by Rosemary and built by her drone forces, appearing in La Femme Rosemary.  Apparently, Rosemary had wanted her own castle since she had been a little girl, and the Black Rose filled that desire.
A large structure designed to look like a closed rose top when the entrances were sealed, and bloomed when the entrances were open.  Many passages existed within the fortress, and its defenses were excellent.  A myriad of environments and traps awaited any intruders who made it inside.  Virtually every room in the Black Rose was under the control of Rosemary from her command center.
After tracking their friends location down, Jake, Fawn, Diana, Jessica and Sarah found the Black Rose and accepted both Rosemary's invitation and challenge of making it to her to save everyone.  She used traps, students, and her own friends against them, eventually enslaving or imprisoning four of the group while leaving Diana for dead.
After Diana confronted Rosemary and was able to knock her down, Rosemary, facing immediate capture, activated the self-destruct sequence for the Black Rose to both cover her escape and hopefully destroy any evidence against her.
Upon witnessing the destruction of her new home from a distance, Rosemary swore revenge on Diana.