Ok so I'm massively behind on this as well but I'm going to write about the new alien species we encountered in the recent series of Torchwood: Miracle Day and hopefully soon I'll get round to Doctor Who and SJA too!!
But one thing at a time!
A fairly generic name for this beasty. They chucked this one in to keep us sci-fi fans happy with the generally spy-thriller and not so Sci-Fi running of the show. These are bog-standard alien wormy things, but they did the job of creepy monster in a box very well. It was interesting that they were a tool of the Trickster, in that he can use them and make deals with mob bosses to change the course of the 21st century but is himself limited in making deals with people and can be defeated by a noble sacrifice. I hope the end of SJA doesn't mean we see an end to what I still think is one of the best villains of the Whoniverse.
Brain parasites are a race of beings reviled for their effect on the nervous systems of beings they encounter. On several planets they are reviled, with one exception where they are considered a delicacy. Brain parasites are sometimes deployed as weapons by those seeking to cause chaos.
It's still unclear what the Blessing was/is and I'm not sure if I'm ok with that. I understand the point that the characters can't know everything but to be dragged through ten episodes waiting to solve the mysteryu only to be told 'we don't know what it is' was a little dissatisfying. That said the blessing was cool, the strange crack in the world that seems to run right through the Earth and is alive and influences the development of the human race.
The Blessing is a mysterious phenomenon located at the antipodes of Buenoas Aires and Shanghai, a break in the Earth believed to run through the centre of the planet and has an incredible influence on the human race. It causes immense distress to anyone who goes near it, often resulting in suicide and projects a patterned morphic field that affects the entire human race. When fed Jack Harkness's immortal blood it made the entire human race mortal, only returning the people to normal when fed Jack's now mortal blood. The Blessing was buried in the ensuing conflict and it's mysteries remain sealed for the time being.
And that's it - more on Doctor Who soon!!