Does anyone have information about the time in which these things have been happening?

http://wh40k.lexicanum.com/wiki/Soul_Drinkers

Before 817.M41 or after?

Alex

According to the fellow posting at this website, it takes place after.

http://www.40konline.com/community/index.php?topic=138750.0

I haven't verified the dates here, but I'll take his word for it.

E