The Keshkali were a species nearly removed from time, leaving the Already Dead behind.
The original Keshkali were humanoid, with three eyes and wide mouths.
After their temporal destruction, they were left with little physical existence. They were wrapped in bandages which held their form together; when killed they would collapse and leave behind only the bandages. They were filled with a black ooze, which they could use to control and then kill other lifeforms. (PROSE: The Undertaker's Gift)
The Keshkali were from the Keshkali Ring Worlds. Their star system was destroyed by a temporal fusion bomb, possibly put there by human forces. There were a few survivors, but they barely existed. They became known as the Already Dead and became a group of suicidal soldiers.
The Hokrala Corp sent the Already Dead soldiers back in time to destroy Torchwood. They also made use of them for revenge on the humans. They created the Undertaker's Gift, a temporal bomb like the one that had destroyed their own planet. They set it up in Cardiff and threatened to use it to destroy the world if the Cardiff Rift was opened. In 2009, Hokrala Corp began sending things through the Rift, causing it to open enough to activate the bomb. The Already Dead started to become active.
Ray Banks saw the Already Dead and wrote about them on her blog, alerting Torchwood to their location. Gwen Cooper found Ray and her friend Wynnie investigating the building the Already Dead were seen in and helped them. Wynnie was killed and Gwen was taken, forcing Ray to call in the rest of Torchwood. Jack Harkness and Ianto Jones attempted to save Gwen and shut down the Undertaker's Gift, but they were unable to do so and the Undertaker's Gift was activated. A Vortex Dweller saved Earth and repaired the damage the Undertaker's Gift caused. (PROSE: The Undertaker's Gift)