I really, really, really recommend you wait until Tuesday and go into this totally blind. Trust me, the wait's SO worth it!
I usually read all the spoilers, and am so glad no one's spoiled Reapers because not knowing what to expect made it so much more worth it. There's
hints here and there but it really insinuates something else happened and you truly believe it only to see that's not the case and the hints were there all along.
And towards the end it makes so much sense, all those little pieces of the puzzle fall into place.
Trust me Ultramorph, wait until freaking Tuesday man!
But if you really want to know, I'll drop a hint.
(But much, much smaller and they don't care whether it'd dark or light, only if there's plentiful food and BOY did the Company give them plenty of food on an Agriculture World...)
Why does the company even bother with Xenomorphs?