Taneel BrightBlade: Iono about an epic blackguard. I'm looking more and more towards the idea of Havendash being an "active" antagonist versus Death as the "passive" antagonist, and that would require an eventual face-off with the PCs...
Humanophile: Death is certainly a LN type, and Havendash will probably be LN or LE. I'm not sure which at the moment. As for the undead armies, because I'd definately like them to still be around, perhaps wherever the dead and buried soldiers rise? Perhaps there's a certain method of burial that prevents the body from rising to join Death's army, thus allowing at least some reprieve from an impossibly powerful skeletal army.
The ressurection is inherently magical in and of itself, and it is that which punctures the barrier Death set against magic, allowing it back into the world. In any case, at the level they're at, the PCs have access to some ressurection magic from their cleric and reincarnate (iirc) from their druid. But if they want to play a new character, should one die, that's their choice. As for the idea of other bands of heroes, that's an interesting idea, and one I'm going to be considering carefully.
I definately like the ideas about Death. Although I'm going to keep around the skeletal armies, though probably not as large as I originally intended, as a "guarentee" that the people don't try to rebuild in Havendash's name. On a bit of a tangent though, perhaps the remaining people have forgotten about Havendash's true name, and now he has entered their legends as the "Herald" of the destruction that Death invoked. Although certainly the PCs, should they attempt it, will probably be seeing tangible sings of their progress in communities/etc, but first they'd have to destroy/drive-off the undead presence in the area. Havendash will definately be an end-game antagonist, and I like the idea of him scheming, with the return of his magic, and putting the world at risk for another round of Death's vengeance. And I'm definately thinking about how/why to bargain with Death. Though I haven't come to any good conclusions yet...
Oni: I'm not sure about why Death wants Havendash, that I'm still working on. As for the other powerful entities, effectively, no. IMC the most powerful "entity" is the land itself, which gave birth to the gods of creation, but they have long since left the mortal races to their own ends.
The Mad Kaiser: I'm starting to like the idea of some unhappy intelligent undead that might be willing to aid the PCs to an extent. The ideas about new diseases is very interesting. Do you know any such resources that deal well with them? Vermin swarms and giant vermin also sound like they'd help give the setting a bit of a distinguishing flair from the normal, average fantasy setting, so consider that idea adopted

And the effect of negative energy? Oooo... I can see not only twisted flora/fauna but even the landforms etc... And the character goals/adventure ideas are really cool
Rl'Halsinor: I can certainly see the idea of the PCs power being exaggerated throughout a thousand years of legends, and that would certainly be an interesting point of RP. As for the question, I think I've decided that the undead have been acting passive. Imagine the main bit of the continent has turned into a sort of bone-yard with skeletons every-so-often. Now, these skeletons are Death's army, and have programming to remove any remnant of Havendash, including those who have memories of him. This would lead to them animating to attack any who approach witht he memory (even if only from oral legend) of Havendash, serving to turn the main portion of the continent into a sort of "badlands" and a place heavily avoided whenever possible by the remaining tribes.
Dogbrain: Indeed.
Dannyalcatraz: Consider those Niven books officially on my reading list.

I've read some of his other stuff and really liked it. And traveling back in time certainly is an idea, but I'm not sure how much I really want to get into the intracacies of time travel. If it happens, it'll have to have a bunch of rules and whatnot to deal with it. Could you expand a little more about this Omega Man movie and Legion? I've never heard of either, and they sound interesting. And I'll see if I can't dig up that Rifts book somewhere.
Clumsy Bob: That's a very interesting idea about the human cattle. It'd certainly serve to give a darker feeling to the setting, and that's always good

I can see freeing groups of those people and then rehabilitating them (if that's even possible?) as an adventure hook for the PCs.
Taneel BrightBlade: Thank you. Once it gets started, I'll be sure to post a Story Hour.
Patman21967: Go ahead with the yoinkage. And playing a dead-guy... perhaps apon their ressurection, the PCs discover they aren't "fully" alive just yet? And they have some ghost-esque abilities (become ethereal x min a day or such) because of their connection with the grave? That would allow a side-quest for them to "cement" their mortality. And I'd love to run it for you, but I'm in SoCal, which is unfortunately wayyy to far to commute to Delaware :-( As for the map idea, I haven't created one just yet, though I'm hoping to do so soon. I actually tend to use large pieces of paper, and then I just burn a small piece of wood for a bit before putting out the fire and using it as charcoal to write with. I find it helps get me "in the mood" for the mapwork, and then it's just a bit of artificial aging before it looks quite good and is ready for wowing players with
Dogbrain: Havendash will definately end up as an antagonist, but it'd be interesting if the PCs actually tried to enlist his help at some stage. That could raise all sorts of interesting situations.
Patman21967: As for PCs joining forces with various undead, I'm definately going to put that option in, as to whether the PCs would be willing to do such a thing, that's another question in and of itself. Also, the undead have been animated, not so much through "traditional" magic as through Death's will, and since he crafted the barrier that shut-out magic, he can still animate them. Magic, however, was barred from any influencing of the world beyond that, so I imagine that all the magical beasts either died fighting against the undead invasion or wasted away, which would leave their remains. I have this mental image of some of the tribesmen stumbling across the partial skeleton of a Dragon and being in wonder as to what sort of creature it could have been (as such magical creatures would, at most, be a faint memory in their oral legends, which would themselves be focused mostly on the raising of Death's army and the effects thereafter).
Dannyalcatraz: I think I'm going to give each of the PCs an undead-related ability, representing a sort of tie they have with death, which would leave the option of a side-quest for them to fully cement their "mortality"
I think I've decided what the nature of Death's deal was. I'm going with the role of Death being taken up by a mortal spirit in ages long past. Now, this spirit wants rest, but to have rest, a new soul must agree to take up the mantle of Death upon its death. However, the new Death must have mastered dark magics to be able to properly perform the role of Death. So Death approaches Havendash (instead of the other way around) with a deal. Death is willing to offer Havendash 10,000 years of life, and in exchange, Death will tutor Havendash (perhaps once every decade or century) in the dark ways. Then, at the end of the 10,000 years, Havendash will die, and upon his death will take up the role of Death. Death singles out Havendash as a power-hungry being most likely to be willing to take the deal. Now, after the 10,000 years are almost up, Havendash uses the magic Death taught him to perform the ritual turning him into a lich, and trying to cheat Death. Then it's not only a matter of Havendash breaking the deal, but also of Havendash misusing Death's "gift" that incurs Death's wrath and vengeance.
Also, I think I'm going to be using modified Aspects of Nerull (from the MiniHB) as Death's chief agents in the world. I'll also be adding some intelligent undead into the mix who may be willing to help the characters, in return when they succeed some of them will find rest while others (i.e.- vampires, etc) want things back the way they were for easy food, etc...
As for what the characters will be doing, I'm looking at first an escape from the remains of Ironwall to the tribe's lands, followed by a bit of possibly either trying to find another tribe/unite some of them and/or clearing out some of the undead to have a "safe area" to begin establishing permanent civilization. Also there's the issue of magic returning (quests to the remains of cities/mage towers to find magical equipment perhaps? as nobody alive, except the PCs and Havendash will be capable of crafting anything, as they're the most experienced magic users in existance). There's also the option of trying to figure out just why the ancient gods of creation abandoned the world/trying to get them to help out, and the options of trying to bring back some of the magical creatures that used to live in the world to aid in the battle/guarding civilization.
What else can you guys think of? Both in terms of mini-adventure ideas, and possibly any unique undead/artifacts/items/magical effects that would be cool to include?
Also, what sort of abilities could I give the players upon their ressurection that are either tied to "celestials" or "undead" that would help underline the difference between the PCs as heroes, and everyone else? I'm ideally looking for stuff that would make up about +1 ECL, and ideally a unique package for each character. For the record, if it helps, the party is composed of:
9th level Human Druid
9th level Elven psychic warrior
9th level Human Abjurer-Wizard
9th level Human Cleric
9th level Elven Monk