Doomfinger

Mother Doomfinger was a Carrionite who, like the rest of her race, was banished to the Deep Darkness by the Eternals. She had the ability to kill people by stopping their hearts with a single touch, from which her name was apparently derived.

Doomfinger was allied with Bloodtide and Lilith, their goal being to release the Carrionites into the real world. Doomfinger killed Peter Streete when the Tenth Doctor, Martha Jones and Shakespeare visited him in Bedlam. She would have killed them as well, but the Doctor was able to name her as a Carrionite. By naming her, the Doctor banished her back to her kin, leaving her horribly weakened. She was present at the Globe Theatre where Shakespeare's new play was about to be performed. When Richard Burbage unwittingly said the lines to release the Carrionites, Doomfinger and her "family" were in victory, however they were imprisoned in a crystal ball, after Shakespeare, the Doctor and Martha Jones defeated them using the word Expelliarmus from the famous Harry Potter series by J. K. Rowling. (TV: The Shakespeare Code)

Behind the scenes
Doomfinger and Bloodtide make a cameo in the animated title sequence of the second series of Totally Doctor Who.