Donna Noble
The TARDIS is captured by the Daleks and transported to the "Dalek Crucible" — their flagship. Sarah Jane, Mickey, and Jackie surrender themselves to get aboard. The Supreme Dalek orders the TARDIS to be destroyed, with Donna Noble locked inside; in the process, Donna touches the severed hand filled with regeneration energy, causing a new, cloned Doctor to form due to a meta-crisis, which saves the TARDIS from destruction.