So super late Saturday night, someone found this image on the TF2 blog:

http://tf2.com/crsk9.jpg

(the 5 blood drops spell out "TOBOR")
Also the file name itself was in patch notes before as an equip region and no one knew what it meant.

After a mad scramble to find all the parts, some unknown person, on Sunday, at 2:30am (that's 0230 to Jinxter), crafted those items together, and a global alarm sound played on all TF2 servers around, scaring a few people to probably wet themselves. Upon the screen, a special chat message appeared. It was a link to this:

http://www.teamfortress.com/bloodbrothers

Now, very early Sunday morning, I post this here while the internet wonders what Valve is going to reveal very soon.

Here's a nice video on youtube compiling what has been going on with this ARG (Advanced Reality Game) for the past TWO YEARS. I've been following it on their forums, but I'm sure we could all use a refresher. And you might not even have noticed what happened on Friday... watch the video.

I was one of those that wet myself.

tempted to craft this item...see what it is

You can't craft it anymore. Only ONE person was able to craft it, after which the recipe stopped working. The result of that craft was the URL to the web comic.

Valve has replied now with a post on their blog.

http://www.teamfortress.com/post.php?id=8621

I also updated the OP with a nice video.