Board Thread:Skyrim/@comment-108.203.204.230-20150105221722/@comment-1470368-20150321115323

It is actually correct to say that the Dark Brotherhood won't be truly "destroyed".

Even if you kill all of the members in the Sanctuary to end that quest, "Destroy the Dark Brotherhood!", there is no guarantee that more won't come along to replace them.

Evil will always find a way...and if the Dark Brotherhood was so easily "destroyed", it would've collapsed completely during the Oblivion Crisis (or earlier).