Shadmoch

Shadmoch was a planet. Shadmoch was mentioned when Richard Burbage was reciting the spell during the play Love's Labour's Won. It had a hollow moon. (TV: The Shakespeare Code)

Behind the scenes
According to Doctor Who: The Encyclopedia (which this wiki does not consider a valid source) Shadmoch was, like Rexel IV (the Carrionite home world), was a planet of the Rexel System.