Good point- we still don't really understand how that agreement was worked out. Did Craster, who had no reason to keep sons around given his disgusting lifestyle, merely abandon his sons out there to die to the elements and the White Walkers came upon them. Did he somehow actively cut a deal (wouldn't make much sense).
I'm wondering how triggered the viewing audience would be if there was a Frost Maul/Cersei love scene.
Craster always went on about being a "godly" man. His daughters explained the sons were given as an "offering".
We do not know a lot about the old gods of winter. Hell, we do not know much about the god of fire.
Given how putrid some worshipers of the lord of light have been(Mel), in sacrificing people to her god. At some points we have seen her have Stannis burn men simply for not destroying their previous god idols, while leaving others alone for the same offense. She wanted to burn Gendry despite him being a relatively innocent boy simply because he had "kings blood". At her worst moment, having Stannis burn his own daughter.
Of all characters south of the wall, she has shown the most visible displays of power. Immunity to poison, visions of the future(limited), ability to birth Shadow assassins and some other abilities in the books not touched on in the show(Ability to sense a warg scouting Stannis army when he was attacking Mance Rayder in a bird and set the bird on fire, causing the warg to feel all the pain of burning and go mad and also, the ability to cloak Mance in a glamour so they could burn Rattleshirt instead and she secretly kept Mance Alive), and in the show(We assumed the same would happen in the books the moment we read this though) resurrecting jon Snow. She is a total Malefactor at times with an "end justifies the means" mentality.
By contrast, Thoros of Myr is a red priest, nice guy who fights for justice and in a Robin Hood type outlaw band, significantly less powerful that we have seen, but was able to resurrect Beric multiple times and (in the books) and Beric was able to somewhat resurrect the one known in the books as lady Stoneheart.
Same god, vastly different approaches.
Up North(and only north), supernatural powers are also available to folks. Skinchanging/warging, prophetic visions and dreams similar to flame visions, and Bran's personal google search abilities(Show only).
On the WW side, Necromancy, weapons that shatter normal weapons on contact and the ability to disrupt wargs that are scouting.
In the east, we saw limited magic. The warlocks and their illusions with Dany. Bloodmagic to save Khal Drogo. Dany immune to flames. Only death can pay for life was a phrase used both by the blood magic, Dany when she hatched her dragons and Red Priests.
I'm blathering at this point.
But overall, there is proof that characters have some way to make agreements with the others/White walkers (at least a nonaggression pact)and Craster worships some kind of god and had a pact with them. Evil bastard that he is.
Cersei is a stubborn moron, power mad and probably incapable of finding out how to make such a pact, but she would be the sort of person evil enough to give away babies(Maybe even her own, although it would be out of character to sacrifice her own newborn). Qyburn on the other hand would be the sort of sick fuck who could dig up that information through study. He managed to resurrect Gregor into Frankenstein's monster and it was not all by medical means.
