Board Thread:Warhammer 40k General Discussion/@comment-7289991-20130323163014/@comment-5452857-20130701041544

on the orrery, they don't just pop stars. Doing so throws the entire galaxy out of balance and would have unforseen consequences. The emprah didn't really have a choice when he imprisoned he wasn't gonna and couldn't just walk across space to put the void dragon somewhere else, the only choices he would have had would have been Terra, Luna or Mars.

I think the only reason the Necrons would want to free VD would be to break it apart to avoid being controlled again in accordance with the new Necron lore.