You're likely referring to the Dark Brotherhood Chronicles. The status of that mod is very much up in the air from what I've seen.
All that work very likely gone to waste because the leader left, as far as I understand it.
Just goes to show that without a motivational, focused leader constantly pushing, all motivation dies and things fall apart.
I don't know which extender mod you found or how good it is, but I've got one of my own very close to release provided the bugs have been squashed and everyone is happy.
You have!? :drool: *Fires up Oblivion in preparation*
Hmm...I should add a sanctuary to Pell's Gate I guess.