Czisch

"Czisch" was a moniker of an alien baby brought to Cardiff before 2009 via the Cardiff Space-Time Rift.

Appearance and abilities
Czisch took the form of an unnaturally adorable human baby. It was capable of telepathy and mind control, and could plant words and emotions in an individual's mind, as well as seeing their memories. This allowed it to find a host with suitable mothering instincts to be manipulated. Czisch overtook the mind of its victims, allowing them to think of nothing other than how to provide for what they believed was their baby. This was emotionally and physically draining. Czisch made Pam Feerce, who had initially been overweight, increadibly lean and skinny, and when he finally released her Pam confessed to feeling suicidal. Despite being a baby, Czisch was as intelligent as an adult human. (PROSE: The Wrong Hands)

Biography
Czisch was brought through the Rift by its mother, who left it in Cardiff with a Torrosett 51 binary heat-cannon. When Pam Feerce found the baby behind a pub on the Machen estate, the baby took control of her mind and forced her to take care of it. Pam cut off all ties with the rest of the world and devoted herself utterly to taking care of Czisch.

Eventually, Czisch encountered Gwen Cooper and decided she was a more useful host, and so released Pam. It then chose the name Czisch specifically to appeal to Gwen's subconscious. Ianto Jones and Jack Harkness were able to release Gwen from Czisch's control, causing the creature to re-enhabit Pam's mind. Before Pam's mind was completely subsumed, she was able to activate the self-destruct button on the heat-cannon, killing both of them. (PROSE: The Wrong Hands)

Czisch's father later infected Jack Harkness and Gwen Cooper with the Kagawa Virus in revenge. (PROSE: Virus)