The Ravens of Despair

The Ravens of Despair was an extended plot hook written for Adventures in Time and Space: The Roleplaying Game. It provides extensive information about an alien threat called the Ravens of Despair, and then provides five "adventure ideas" that can be fleshed out by the Game Master - Summer Holiday, Hard Time, Mourning Day, The Crest of Corazon, and War and Grief (intended as a direct sequel to The Crest of Corazon).

Publisher's summary
There are some individuals in this universe who follow fear and trouble. They are drawn to it like a magnet, ending up time and time again in places rife with threats and danger, full of enemies at work or monsters at large. They arrive in the nick of time, when all seems darkest. Then there are others, in this wide, nigh-infinite universe, who seem to follow sorrow. They are drawn to heartbreak and defeat. They lurk in the shadows of the darkest of days and the worst of nights. They arrive, and bring the darkness with them. So hungry are they for sadness that they are called the Ravens of Despair.

This supplement for Doctor Who: Adventures in Time and Space includes full rules and background for the deadly Ravens of Despair, as well as loads of plot hooks and story ideas for pitting your own time travellers against their machinations.

Characters
As this release focuses more on providing information for the Game Master to create their own adventures, it does not include any specific characters. However, the following characters or races are included in the "adventure ideas" included in the release:

Hard Time

 * The Master
 * Davros
 * The Rani

Mourning Day

 * The Sisters of Regret
 * Judoon

The Crest of Corazon

 * Atahualpa
 * Corazon

War and Grief

 * Atahualpa
 * Corazon
 * Aguirre
 * The Cardinal

Aliens

 * The Ravens of Despair's goal is to eliminate emotion in the universe.
 * They were created by the Alturons, beings of pure thought that were once composed entirely of psychic energy.
 * The Ravens and Cybermen are allies.

Daleks

 * The Daleks' "perfect hatred" can be diminished by the Ravens' power. For this reason, they consider the Ravens a significant enough threat that, if a Raven is present, they will prioritize its extermination before others.