Look at these
http://darksoulswiki.wikispaces.com/Great+Magic+Barrier
http://darksoulswiki.wikispaces.com/White+Seance+Ring
From these two descriptions, along with information from other items related to Havel, some members of the church obviously have an issue with sorcerery. In the prior game, Demon's Souls, the priests and the magicians never stopped arguing or saying the other was a fool. Magic is viewed in a negative connotation by most of the public and by the church, similarly to how Europe did in our own history. Havel's knights are essentially Crusaders, only that they were warring with Seath-even though he was Gwyn's ally. By adding those two descriptions together, it's certainly possible that Havel was even once the head bishop of Thorolund.
Yes, most undead are Hollow. Based on both the very character you and I play as, as well as many npcs, though, being undead does not inherently also mean being Hollow.
While, yes, at least the Lady Darkling and the Fair Lady chose to become Fire Keepers, that is by no means a kind or easy thing to be-
http://darksoulswiki.wikispaces.com/Fire+Keeper+Soul
The crestfallen warrior, while he's just suggesting a possibility regarding her, gives information about society at large in Dark Souls in his statement, "They probably cut her tongue out back in her village, so that she'd never say any god's name in vain.
How do these martyrs keep chugging along? I'd peter out in an instant." This apparently isn't that uncommon or unheard of-similar enough to our Europe when it's technology was at about the same level, and of society was comprised of similar mindsets.
There's also a list of items that resist the effects of the Dark-purging stones and both types of rings of sacrifice- that are created from human sacrifices. Please note that the bonfire keepers and the Chosen Undead technically are these as well-they just don't get to die.
As for my statement on wars-if they were only killing hollows, then they wouldn't be using so many swords, polearms, heavy steel armor and such; those, at least in our own world, by trial-and-error and the practical uses of arms and armor. Most of the weapons and armor presented is meant for killing living people; there simply is no way that the amount of tools of warfare present would have been created if there was no war. Therefore, the human nations being led by the gods apparently aren't so peaceful; rather, they seem to engage in about the same, or perhaps even more, armed conflicts than did Europe. And, again, considering content from Demon's Souls, and that there is a heavy Berserk influence, (among others) it would just be odd if there was little war. Here's a quote from a merchant in Demon's Souls in regard to the kingdom being overtaken by demons and the men all being driven mad when his soul was eaten; "But hell, at least the demons don't send us to our deaths in battle!" The main character of Berserk, Guts, was a mercenary for his entire life before becoming a demonslayer. And, considering how dark Dark Souls is, I really think there's war going on. If kind, benevolent and wise gods are leading humans, then there probably would be little war.
In regards to the proposition that demons and other monsters are in the mainland-there's nearly nothing, if anything, to support that. There are only two demons even outside of Izalith in Lordran, which is pretty small. There are no item descriptions, though there are plenty of the incidents regarding undead.
Also- http://darksoulswiki.wikispaces.com/Darkmoon+Blade+Covenant+Ring
If this is blasphemy, then the presentation of the gods and religion certainly seems to be a bad one. While, yes, Gwyndolyn is possibly more mentally unstable than most of the other deities, at least he's still there; the others just up and left. Anor Londo, especially after quotes from Oolacile, was the city of the gods. Based on quotes from Gough, Ciaran and the entire feud between Fire (gods) and Dark, (humans) it seems that gods and men mixed as little then as they do in the current day.
I also wonder what
There actually is one character who is blatantly glad to be undead, though, likely less so after he goes Hollow-Laurentius. "In this land, pyromancers earn a certain respect.
The Witch of Izalith, one of the legendary Lords, is the godmother of pyromancy. So, the day I became Undead, I was ecstatic. I felt as if I'd been chosen to attune myself to the ancient arts. … Of course, it wasn't all that romantic in the end…"
And Solaire, while not happy about being undead, is apparently quite willing: "I became undead to pursue this..."
Ultimately, I think that From set out to make a similar situation for the ending of Dark Souls as with Demon's Souls. In Demon's Souls, after seeing the world and all the atrocities in it, you finally find out how and why demons followed Old King Allant from his secret journey; he became convinced that the kindest, most merciful thing he could do for the world was to end it. He purposefully awoke the Old One, essentially literal Nothingness with a will and an infinite apatite for souls, that would, left to its own devices, eventually erase the world itself. The court was apparently very corrupt even before there were demons; the miners of Stonefang worshipped a demon dragon as a god, even though society avidly followed a single God similar to the Abrahamic one. Latria seemed to be a prison even before there were demons, and was actually taken over as revenge. The shrine of storms was a long-dead land of men who worshipped wind and death; they practically lived only for the honor of dying. And worse yet, was the Valley of Defilement. It was a land filled with lepers, criminals, plague, monstrous insects and leeches, towering waterfalls of plague-ridden blood, swarming with unborn fetuses that attacked anything that entered-and that was after a living saint, Astraea, became a demon, entered the Valley, and actually improved the conditions.
At the end, the player is offered the choice; does s/he lull the Old One back to slumber and save this terrible world? Or do you aid the Old One, for greed or for a suicidal mercy? The game intentionally raises the question of whether or not the world should be saved. After considering all the information in Dark Souls, I think it raises the a very similar question: is Fire and the gods worth saving? FromSoftware intentionally gave no clear answer.