Morjanus was a soldier who came to Earth to test experimental new weaponry to aid her people in their fight against the Hunters. She was followed by Jack, a Hunter who wanted to stop her. To avoid him, she assumed the identity of "Penny Chapman".
Arriving on Earth, Morjanus attached a proto-morphic lifeform to the gasworks. She housed the lifeform in Blackthorne Gasworks, London. Finding that a Hunter called Jack had followed her, she used self-hypnosis to make herself believe she was Penny Chapman.
For three years she waited for the lifeform to fully incorporate itself into the gasworks, living her life as Penny in a London flat on Latham Lane and working at Blackthorne.
One night, Penny was out in London when the Eighth Doctor bumped into her. He tried to assist her but found her to be in a trance, muttering about "the essence". Penny cried out in apparent pain and the Doctor was accused on harassing her. At this moment, Jack appeared and moved to attack her, as he had many women on his search for Morjanus. The Doctor saved her and, once he was gone, Penny vouched for the Doctor, telling Inspector Porter that he had not attacked her.
Worried for her, the Doctor escorted Penny home. He told her tales about his trip to Egypt and Penny told him that she had grown up in Essex but moved to London to "see the world". Once home, the Doctor promised to check up on her the next day a fact that pleased Penny.
Shortly after, she saw the Doctor fighting with Jack outside her house and used her landlady's gun to attack Jack, fending him off. The Doctor entered a nearby carriage, preparing to leave. Penny decided to join him and he welcomed her. They travelled to the Doctor's TARDIS and Penny entered it, amazed at its size within. The Doctor opened a map and found that Blackthorne was the source of anachronistic technology.
The Doctor and Penny went to Blackthorne and she used her key to gain access. Within, Penny fell once more into a trance, opening a padlocked door with the touch of her hand. Within was the lifeform and Penny held her head, memories flooding back to her. She told the Doctor that the Pyrodines had been released. He tried to help her but she had fully regained her memories.
Morjanus knocked the Doctor down and, threatening him with the gun, forced him onto the roof. There the Doctor told her he had fallen for her guise but she told him she had believed every word, as if she had been Penny. As she no longer had a purpose for him, she raised her gun and fired, only to find it unloaded. The Doctor showed her that he had removed the ammunition in the TARDIS, unwilling to enter Blackthorne with an armed hypnotised girl. Instead, she tried to have a Pyrodine kill him but Jack appeared and used his bare hands to fight it off.
Morjanus bent a metal pole in her hands and threw it at the Doctor, knocking her near the edge. She then attacked him but he pushed her over. Managing to gain a foothold in the wall, she climbed back up and chased after the Doctor. Morjanus was unable to stop him destroying the lifeform and tried to kill him. However, Jack attacked her from behind withhis psychic powers, knocking her down.
When she awoke, she was Penny once more. Jack had removed all the memories relating to her life as Morjanus. The Doctor advised her to return to Essex, telling her the London wasn't safe, even with Jack as its guardian demon. (COMIC: The Curious Tale of Spring-Heeled Jack)