The Holomorph
From Tardis Wiki, the free Doctor Who reference
The Holomorph was an intelligence imprisoned on Zoda-Kappa. A hundred thousand years later, in 3895, they used Professor Charles Feige to find a way to escape into the Dream. However, it was defeated by the Sixth Doctor, Melanie Bush, Hebe Harrison, Lydia Betancourt and Sakho Cato and returned to its imprisonment. (AUDIO: The Dream Nexus)