Qwerm

The Qwerm were a race who allied with Gallifrey in the early years of the universe. They assisted them in fighting the Great Vampires. The Qwerm feared that they would eventually be attacked by the Time Lords, and hatched a plot to defeat them should it ever happen. The Qwerm attacked their Time Lord ambassador in her TARDIS, and created a nest inside, planning to attack Gallifrey in the future, once their empire had become complacent. The Time Lord ambassador, Rocinante, placed her TARDIS in a time loop to stop the Qwerm's plans, and signalled for another TARDIS to help her. The TARDIS caught the attention of River Song, who aided Rocinante to connect the TARDIS' front door to its back door, trapping the Qwerm inside forever. (PROSE: River of Time)