Eknodine

The Eknodine were a species of aliens that took over the bodies of old people in a dream created by the Dream Lord.

Biology
The Eknodine were aliens that could live inside of human hosts, extending their lifespan. Though most of the body of the Eknodine was hidden inside the human host, a green eyestalk could be extended from the mouth, which would spray out a green cloud when attacking. This cloud could turn humans into dust. (DW: Amy's Choice)

History
The Eknodine that the Eleventh Doctor, Amy Pond and Rory Williams encountered said that they were driven away from their home planet and came to Earth, where they took hosts at the Leadworth retirement home to stay inconspicuous. Angered at their loss, they decided to destroy other worlds.

They chased and attacked the Doctor, Amy and Rory after they found out what they were and cornered them in Amy and Rory's house and attempted to gain entry. One, in the guise of Mrs. Poggit, killed Rory after she climbed to the top floor window, and turned him into dust.The Doctor used a lamp from the baby-to-be's bedroom to make the Eknodine fall from the roof, presumebly killing it. Amy and the Doctor decided to kill themselves, hoping that this was the dream, and used a van to run a couple of Eknodine over, before crashing into the house and 'dying'. (DW: Amy's Choice)

Behind the scenes

 * "Ha'rik" may have been an unused name for the Eknodine, making them one of the three new enemies to appear in Series 5.