Sweet Salvation / Seizure
The Ravenous were a race of creatures from the “old times”.
After defeating the Kandyman’s and the Eleven’s scheme with the thought spider, the Eighth Doctor and his companions caught of a glimpse of faces reflected in glass, screaming, and Helen Sinclair saw a word in her mind: “Ravenous.” Afterwords, the Eleven mused to himself that he knew what they fed on, and that all anybody could do was run. (Sweet Salvation)
The Eleven was later found by one of the Ravenous onboard a dying TARDIS which he had stolen. The Eleven was scared enough to call for the Doctor’s help escaping it. According to the old tales, the Ravenous ate temporal energy, with Time Lords thus being their most potent source of ‘food’, while shorter-lived life forms such as humans would be little more than the equivalent of a packet of crisps to satisfy the Ravenous’ appetite. After the Eleven stole the Doctor’s TARDIS, the Doctor was able to escape the Ravenous by using the last of the dying TARDIS’s power to make a random materialization, leaving the Ravenous in the TARDIS to be destroyed as the ship’s interior dimensions finally collapsed. (Seizure)