I've looked around a little and couldn't find answers to my questions, so I was wondering if someone could help me out. Feel free to skip over the parts not in bold, they're really only for clarification and get a little long in places. I'm a little new to the world of Eberron (only picked up the books a few months ago, I avoided it as a setting for years because I wasn't sure how to feel about the technological aspects such as the lightning rail) and there's been so much material to get through and absorb, it's really nice but a bit overwhelming. Sorry if some of these questions are dumb and/or I seem misinformed. I'm just really curious because positive necromancy seems like an interesting concept.
1. What separates positive necromancy from its negative counterpart?
2. Do those risen via positive necromancy always retain control of themselves regardless of the necromancer's intentions, or can the necromancer choose to force them into servitude as with normal undead? I've read that the elves of Aerenal despise the creation of mindless undead, but that doesn't necessarily mean that it isn't possible to raise mindless undead with the kind of magic that they use (as far as I can tell); it just means that they don't use it that way.
3. Does someone have to be good (or at least not evil) to utilize positive necromancy, and if so will they lose their powers if their alignment shifts, or will their spells simply change from being fueled by positive energy to negative?
4. Do undead raised via positive necromancy remember their lives? What I've read on Aerenal made it sound that way to me, but I don't remember it ever explicitly stating one way or another.
5. I read something about positive undead (undying, deathless) being sustained by devotion, is that a hard rule for all positive undead? If so, what could possibly count as devotion? Could such an undead masquerade as a living hero beloved across Khorvaire, and be sustained simply by the adoration of the people? Would it have to be more precise, like a positive undead posturing as a prophet and leading a minor cult to feed off of their devotion in person? Or is there some archaic ritual that must be performed by members of the living in order to allocate "devotion" energy towards sustaining a positive undead? (Or is it enough for a positive necromancer to just zap them full of positive energy every now and again?) Or is the whole notion that these undead require some sort of sustainance just what the Aereni choose to believe?
6. Would there be any positive necromancers/positive undead among the ranks of the BoV? I remember reading something about the order revering intelligent undead. Does it only revere those raised by negative necromancy, or...?
7. Why is positive necromancy generally only practiced by the elves of Aerenal? (As far as I know, please correct me if I'm wrong.) Is it because they aren't close with the races of Khorvaire and so none of the other races have picked up on the how-to of it, or is it that Aerenal's "closeness" to the realm of positive energy makes this kind of magic possible on Aerenal only? I remember reading that the City of the Dead is the only place where the ritual of the undying can be performed, and while it doesn't explicitly state that the reason is magical limitation rather than time-honored tradition, I feel the former is more likely. But that only counts for the special ritual they perform to turn their revered countrymen into undying, which seems like it would be an intricate thing whereas a simpler spell in the same vein might be cast without being in or near the City of the Dead.
8. Assuming that positive necromancy is only accessable in the City of the Dead, would it be possible to charge an object meant for storing magical energy with enough positive energy to be able to perform positive necromancy elsewhere (such as on the mainland of Khorvaire)?
9. The Tairnadal seem to commune with spirits, is this a form of positive necromancy? If so, can this be taken as evidence of a form of positive necromancy that can be performed away from the City of the Dead (assuming positive necromancy is generally only accessable in the City of the Dead)?
10. What is the correct term for positive necromancers? Or is that what the Priests of Transition basically are?
Kemeshvara wrote:
To add to that:
Tempest_Stormwind wrote:
All of Tempest's answers are good, so I'm only adding where I feel I have something to add. In my opinion, Aereni necromancers employ both positive and negative energy. While it's never been called out, I could see a number of necromancy spells being reflavored to suggest that they are using positive energy - notably False Life. A Mabaran version of the spell might give the caster unnatural vitality, whereas an Irian interpretation might fill the subject with excess life-force that automatically heals wounds. But an Aereni necromancer typically understands both forces and can draw on both.
The Blood of Vol, the Undying Court and the faith of the Tairnadal are different answers to the same question: How do we prevent our greatest souls from being lost? The Undying Court was developed as a way to preserve the greatest members of Aereni society. But as noted above, if all the Aereni were slain, the Court would go with them. The Tairnadal provide a more metaphorical immortality, with descendants acting as avatars of the past heroes. This has the same problem: if all the elves die, the heroes are lost. Thus the line of Vol pursued Mabaran undead. No one gives anything to a vampire; she takes what she needs to survive. According to Aereni belief, while a lich doesn't feed in as obvious a manner as a vampire, it is still sucking life energy from the world itself to sustain itself. This is why the Deathguard consider the Mabaran undead to be abominations: they are hurting the world just by existing. The BoV evolved from the beliefs and practices of the line of Vol, so no, you shouldn't find Deathless there; it's a fundamentally different approach.
As for why it's not practiced elsewhere, there's a number of reasons. First, it requires a close connection to Irian to perform the greatest feats, so it's simply not possible in most places. Second, one of the basic principles of Eberron is that magic behaves in a scientific manner. Why doesn't Zimbabwe have nuclear weapons? You need to have the raw materials required and you need to know what to do with them, and neither of these things come easily. Per most canon sources, it took the Aereni thousands of years after arriving on Aerenal to figure out how to create the Undying Court... one reason Aeren herself isn't part of the Undying Court. So even if you dropped Irian manifest zones into Khorvaire, that doesn't mean that they could figure out how to make Deathless.
With that said, it's not somehow unique to the elves, and another society could figure it out. In the Eberron computer game Dragonshard we had the a clan of dwarves from the Demon Wastes that had a Deathless tradition - again, with the idea that they lived in an Irian manifest zone and had developed the tradition over time.
And I wouldn't equate the Tairnadal practice to the Undying Court. As Tempest says, it's more shamanistic (and in 4E, I had a player make a Tairnadal shaman with the idea that he was working with patron ancestors). Again, the point was that Vol, the UC and the Tairnadal all found different answers to the same problem.
Thanks so much everyone! This is exactly what I was looking for. Eberron is my dream campaign setting that I never knew I needed until recently. I love that it seems like there's always more to learn about the world, and definitely no shortage of engaging adventures waiting to happen. I hope my players are having as much fun adventuring as I'm having learning about the world 
Tempest_Stormwind wrote:
Kemeshvara wrote: