All your women are to be raped if you don't join the Horde.
The sky is not black yet, it means that you still have a priceless time to think all the things over and make the right decision after all.
You will regret your hesitancy when the sky be turned black like ink and our horses come to your plastic city. What shall you do when the Khan with the golden sun-swastika on his banner takes your sister, your mother, your beloved girl or wife? What will you say when all your false dignity be vanished away and the inside nihilism revealed? Your dammed soul can't even be sacrificed.
So, if you are the worthy one - join the Horde! Create with us, destroy with us! Live with us, die with us! Be the part of us!