Board Thread:Warhammer 40k General Discussion/@comment-67.197.44.118-20130216115719/@comment-2093048-20130401034232

Dark Angels were loyal according to the Horus Heresy books. The Lion got delayed because of Night Haunter, who then taunted him that now everyone would forever question the Dark Angels' loyalties. Lion's response was that loyalty was its own reward.

As another point for the Alpha Legion, even if they were loyal (though again, the whole reason for them siding with Chaos to destroy Chaos kinda flew out the window when Horus lost, anyways), I find it rather doubtful that Tzeentch wouldn't have figured out their plan to destroy Chaos by now (...whatever the hell their plan is now, considering that the original one went out the window when Horus lost, anyways).

Really, the entire reason they joined Chaos as far as we know was so that Horus would win and then Chaos would eventually be destroyed by Horus after that. And as we all know, Horus lost. Yet the Alpha Legion is still with Chaos. So like, the heck?