If Nemesis was so vocal about being the only god, why would Lethys team up with him if he knew that Nemesis would eventually kill him?
Lethys teamed up with Nemesis to keep Nemesis from killing him right away. He probably was hoping he would be spared or that he could find a way to survive somehow.
Maybe Ol' Blue had plans of his own, after disposing of your annoying red-boy butt.
Also, despite the veiw, the gods are still "human" but with a different perspective. The threat of being "mortal" seemed to disturb Lethys greatly, to pleading with you and giving up a treasure, which Nemesis himself wanted to avoid others having, at the threat of dying. He might have been persevering himself, and things like robbing your creature might have been desperate attempts at prolonging your fight with him, giving himself more time to live as he was still trying to take out another god and still not a rival of the "powerful" Nemesis.
Nemesis and Land One
Nemesis attempts to kill the player on Land One by attacking the village. Why didn't he: A, go for the other village as well, B, attack the temple/Creature, or C, attempt to attack the player on any of the other lands?
That bugged me too, especially when he destroyed Khazar so easily and completely ignored the player.
You were an afterthought perhaps? He was just working down a list of possible threats and you, the new and low-powered god, were somewhere near the bottom. Not much of an explanation, but I imagine killing Khazar or ex-Nemesis creature was a lot harder than it looked.
In the last level he says he 'enjoyed your successes', because there's nothing in killing a lower god for no reason (obviously Khazar was a clear threat and Lethys was a traitor). So he was probably hoping you'd come back stronger so there'd be more glory in killing a powerful rival.
As well as the "Not Worth Killing / I Need You Stronger" aspects as noted above, which are both fair points, there's another factor. Look at it from a gameplay point of view, because Nemesis is (supposed to be) the same kind of God as you, with the same restrictions (the only time he clearly doesn't, killing Khazar, he's using the power of a Creed). He's working in a land with NO worshippers, remotely (so he has no Influence in that land, and is essentially just throwing attacks/reaching out through a vortex). The total mana cost of the miracles used in Land One was not insignificant. Lightning Increase/Extreme on the Creature, high-powered Storm on your village (which lasted for quite a while, and in gameplay the Storm costs a constant stream of mana)... it WAS a serious attempt on your life, or at least intended to slow you down so he could recharge and come try again later, and would have crippled you had Khazar not intervened. He may not have noticed the second Village, given that he was working remotely, or might have just not had enough reach or mana. In Land Two, his vortex is targeted on Khazar, and is far away from you. He could not have possibly reached out to you, and nobody could possibly have good enough aim to fireball you from that far away. After his assault on Khazar, he probably didn't have enough power to vortex over to you right away. He uses several high-powered miracles against Khazar, and we have to assume two vortexes in a row is beyond even Nemesis. Plus, he thinks Lethys can beat you (and if Lethys can't, then you're strong enough to be fun to pwn when he gets around to it). Bottom line: He's very powerful, but not omnipotent.
Humans and Non-Benevolent Gods
If gods in this game die when they have no followers, why don't the humans agree to only worship benevolent gods?
If you knew that God only definitely existed, but could literally drop a two-storey tall ball of fire on your house at a whim, conjure magic lighting, and otherwise bring his terrible wrath upon you at even the slightest hint of desertion (remember, you can monitor belief in this game) would you honestly believe that everyone would agree not to worship such a being?
One problem with that plan, actively choosing not to worship a particular deity requires you to acknowledge their existence. I'm not sure what the rules on what constitutes worship but since you can continue to exist without active worship I think it's safe to assume that people who believe you exist are enough to keep you alive even if they choose not to actively worship you to avoid giving you the ability to kill them. Which defeats the entire purpose since you can still kill them and scare others into falling in line.
For the same reason you still do what a Jerk Ass boss tells you to do, or a particularly scary gangster, or follow the speed limit when driving in front of a police vehicle, or stay the hell away from a bear that's attacking your campsite.
Besides, these people? The apathetic, near-vegetative morons, who cannot agree to screw until your divine hand personally puts plug A into slot B? I don't think so.
You are all forgetting the ability to sacrifice people for belief.
Remeber, you're seeing this from a God's perspective, someone who can look over the whole land at will, knows the full story and true nature of Godhood, and is immortal unless killed. Look at it from the mortals' perspective:
They don't know any other way/Gods. Take Lethys' primary village in Land Two. Probably all its inhabitants know is Lethys' reign. They've never heard of the war between Lethys, Khazar (and You). Even if they know that Lethys isn't the only God, most would not know that there are other Gods active in the Land. Homelessness, hunger, cold and Lethys are all equal parts of their world. They can't concieve any better. Plus, a lifetime in game is less than half a real life day. Most people in the game live or die only knowing a single God, not knowing about the battles between Gods unless they're on the front line.
Additionally, better Jerk Ass Gods than no Gods? Most of the AI "Evil" Gods are closer to Pragmatic Villainy than Stupid Evil; they're not Card Carrying Villains who do things For the Evulz. Take Lethys for example (and I think Nemesis too); he expands and looks after his villages, even if ruthlessly and minimally, and never attacks his own people (unless aiming at your invading Creature). At best, they see him as a positive figure, building homes and providing food, no matter how little. At worst, they see him as a cold-hearted, cruel, invincible, and incomprehensible tyrant.
It's one of the greatest flaws of human nature that we will follow some complete assholes just to fit in. Look at any dictatorship in history: Stalin in particular was pretty cruel to his people, what with the purges and all, yet nobody wanted to be the first guy to rise against him because that person would be killed. Now imagine the compliance of Soviet Russia (or Nazi Germany, or modern-day North Korea), except back in ancient times when information was much, MUCH easier to control, and also the ruler in question is an omniscient, immortal deity with a King Kong Death Monster at his disposal.
For the people that played all of Black and White: Creature Isle...Is "The Source" a case of Urban Legend of Zelda or Guide Dang It???? Because after getting the ring of the Brotherhood and THEN fighting everyone in the dojo for the Gauntlets of Power nothing seems to change at all and there was a screenshot going around that demostrates that your creature can use the telekinesis power of The Source in combat but nothing that I do in the isle seems to imply any change or progress or being able to do that, nor is there any hint in the scripts. So, what is it?
AND speaking of the script from the Vanilla game, those First Person toughs of the creature that describes to itself the action it is doing. WHY is it doing it, a case of Dummied Out or Guide Dang It? Because I find it HARD to believe that something THAT important was Dummied Out. It's a pain already to see the same message of "your creature wants to be kind and generous" just to discover that it's something that he does for reasons that comes right the fuck out of nowhere and wasn't EVEN inspired by my teaching.
Your Creature is smarter than you think. When you reward it for something, e.g. casting a resource miracle into your village store, or killing an enemy villager, you not only encourage that action, but also related actions (encouraging one kind and generous action encourages others, as does encouraging one angry/destructive action). So, for example, in the former case a creature encouraged to provide resources will also create breeders (which is considered to be kind and generous, as it addresses the population desire flag), or in the latter case a creature encouraged to kill people will also destroy buildings.
If your Creature is a Tiger, the massive Guide Creature in the first land is a Lion. On the final land, Nemesis' Creature is also a lion, and is the same size as your own, i.e. much smaller than the Guide in most cases. Apparently, Nemesis ditched the Guide Creature because it was too weak. I know the Guide also claims to have been too cowardly for Nemesis, but he stands up to him in the end... really, why didn't Nemesis just keep the Guide Creature?
It's said that your, the Player Character's, creatures see you as good, no mater if you beat it within an inch of its life constantly or make sure it's well taken care of. As the guide seemed to be DIRECTLY disobeying nemesis he may have ditched it and gotten one that would listen. The only reason he would strike down the guide later is because, rather than just disrespecting, him he was, in Nemesis' eyes, directly working against him now. The new lion was a good little kitten and listened much better than the guide would have.
Nemesis and Land Five
Since Nemesis must live up to his namesake, if you're a good god the game calls him "the embodiment of evil," while if you're an evil god he's the ultimate good guy. Problem is, this distinction doesn't change any of his in-game behavior — no matter what, he's ruthlessly determined to wipe all other gods from existence, killing hundreds of potential followers, especially on Land Five when he tries to slaughter his own village after you convert the people to your side. At any rate, he's DEFINITELY a far cry from good...