Well the new series is well on it's way with a cracking two-parter and some interesting episodes to follow. As ever I'll be discussing any new aliens that appear over the course of the series and that will be the focus of my posts - for more discussion of the episode as a whole please visit Impossible Podcasts in the sidebar for commentary and opinion by my good friends in Cardiff, one podcast even features Me!!
Anyway, on with the new series.
These were a great start to the series, the concept of a monster that can make you instantly forget them was brilliant and they served as fantastically creepy monsters. Their global conspiracy was interesting too, only ultimately we don't really know what they were up to. Similar conpiracies are uncovered in comic series' like Planetary and Marvel with Secret Invasion, but there is always a goal - we have yet to see the goal for these guys and even though they got wiped out nearly I'm still hopeful that we can see their end goal sometime soon.
The Silence are a mysterious race about whom almost nothing is known, this is due to their ability to make people forget them as soon as they pass out of sight. They have had a presence on Earth for millenia, shaping human civilization to their will, using hypnotic suggestion to drive humanity to build devices that are of use to them. Their ability was used against them when the Doctor sent a post hypnotic suggestion that caused humanity to rise up against them, though they would never remember it.
No, not the Siren, she doesn't count because she's an AI!! The Siren was a medical AI for a group of Aliens that got stuck in out dimension and killed off by human bacteria, War of the Worlds style. They had horse-like skulls and other than that we don't see anything about them, which winds me up no end - in my opinion you shouldn't put an alien (or spaceship/planet/anything) in a Sci-Fi show without being prepared to include an encyclopaedia article about it somewhere!!
The Siren worked for a race from another dimension, humanoid but with very different features from humans, they became trapped in the Doctor's dimension and killed off as foreign contaminants accessed their ship through dimensional gates. When they were dead the Siren went through the portals between their world and ours and took on human form, taking any injured aboard her vessel for treatment.