Malevilus

The Malevilus were a malevolent winged race of bat-like humanoids said to feed off death. They possessed a range of powers from shape-shifting to low-level reality warping.

On an alternate Earth, five Malevilus named Babiyon, Abiss, Epok, Nekros and the most powerful - Magog, took on the form of Roman gods and supplied the Roman army with advanced technology. In return, the Romans offered up prisoners to them for sacrifice. The Malevilus set up puppet Emperors in their stead and oversaw the expansion of the Roman Empire throughout the Mutter's Spiral.

The Fourth Doctor ended their rule by televising the image of Magog and showing the Roman people the true faces of their "gods", inciting them into open revolt. Magog was trapped in an empty dimension within the Doctor's TARDIS, and the rest of the Malevilus tried to escape in their spacecraft, which exploded on take-off, killing them. (COMIC: Doctor Who and the Iron Legion)

Behind the scenes
The Krillitane from the episode School Reunion strongly resembled the Malevilus.