Board Thread:Warhammer 40k General Discussion/@comment-14745711-20130906234048/@comment-6078851-20150503160620

while an interesing idea i too havn't heard of the watchers being part of the cabal. but i really like the idea that the watchers are the old ones, and while it's probably unlikely there could be some merit to it:

among many of the canon theories regarding the fate of the old ones there's one which theorises that gretchin are their direct descendants whose intellect has diminished over the millenia. the watchers in the dark are of a similar stature to gretchin (and no-one's ever seen their faces), but maybe they are 'pureblood' old ones and their intellect has remained formidable. although if they are all that remains of true old ones and are guiding the dark angels to something then it doesn't matter what the dark angels think - the watchers don't talk to anyone, vocally or psychically, and despite the fact that they are a part of the dark angels the dark angels know, literally, almost nothing about them.

they probably aren't old ones, but it's an entertainingly plausible idea :)