The Adherents of the Repeated Meme were cloaked in black and concealed behind masks with grated visors. They had metallic arms and wore livery collars. (TV: The End of the World)
These androids were used to carry the metal spiders and to allay suspicion away from Cassandra at the end of the world party, where they supposedly represented Financial Family Seven.
Cassandra also had them knock Rose Tyler unconscious and drag her in a room with its sun filter descending as revenge for insulting her earlier. The Adherents were discovered and shut down by the Ninth Doctor when he ripped off one of their arms. (TV: The End of the World)
Behind the scenes
The Adherents' only appearance is in The End of the World, the first episode in which the repeated Bad Wolf meme is adhered to. Their name is most likely a reference to that plot device.