Kotturuh

The Kotturuh, or the "Bringers of Death", were a species from the Dark Times who could bring an end or apply a limit to the lifespan of other species. (PROSE: The Guide to the Dark Times)

Biology
The Kotturuh were immortal, with the ability to grant (or enforce) a defined lifespan upon an entire species - from thousands of years to instant destruction. They typically wore robes which concealed their tentacled lower halves. (PROSE: The Guide to the Dark Times)

Culture
The Kotturuh saw death as both their religion and their gift to other species. (PROSE: The Guide to the Dark Times)

When the Doctor was planning on blowing up the Ark of Whispers to prevent it from crashing into a planet, Benny mentioned the Rites of the Kotturuh as a piece that may be aboard the mythical ship. (AUDIO: Have I Told You Lately?)

History
The Kotturuh were among the first species in the universe. After a while, they set out to distribute death among the denizens of N-Space. They were known to either visit worlds peacefully, before allocating lifespans to the natives of that world, or else they would simply destroy life on a planet without so much as a word.

Many species attempted to flee from the Kotturuh, such as the Eternals, who sacrificed their ability to lead their own lives in the process, hence their reliance on Ephemerals. The Racnoss, meanwhile, went into hibernation to avoid their destruction.

Other species attempted to negotiate - The Osiran, Sutekh, bargained with the Kotturuh for the gift of death; the Great Vampires managed to keep their immortality on the one condition that they must feed on others to sustain their existence.

The Dæmons tried to fight back, but the Kotturuh were too powerful, leaving only Azal, who fled to Earth to live in suspended animation. (PROSE: The Guide to the Dark Times)