Thank you, but I’m nowhere near a master haha. Maybe an enthusiast though.
I have a better question. If Griswold became a zombie, can Tyrael become a zombie too?
See that’s what pissed me off about D3 and its butchering of the lore because they wanted to move away from christian themes to move into some other fantasy.
They removed christian elements and gothic architecture and good music to bland open area’s with crap music, in my opinion.
I’m not religious or anything and most people would tell you I’m an atheist but I enjoy fantasy around myth’s that exist in the real world and not some garbage high heavens that we got. I liked the feeling that all good and righteous beings abandoned us but one angel and he was here to try and protect humanity because he cared.
Removing him from the equation and on top of that turning him mortal made no sense and then introducing more angels that previously never showed themselves all at once was jolting and immersion breaking.
I want to be on a desolate world filled with powerful minions of hell and feeling hopeless. Bosses need to come out of nowhere in RNG worlds and not stuck in some arena with no chance of escaping unless you kill them, except say the last boss because that makes sense that the final big bad set’s a trap for you in hopes you obliterate you.
For some reason the members of this forum get mad at me because I don’t love D3 and label me as a troll when in reality I’m not one and am just a very harsh critic of the 3rd game and feel that it let down everyone and the people too blind to see it are the same kind of people that wouldn’t fight for independence and freedom because they’re happy with the soylent green the government feeds them, happily in gleeful ignorance.
Did he technically become human or just mortal.
Technically powerful Demons, prime evils and their kin, as well as Angel’s and Nephalem can will thing in and out of existence. So if Diablo really wanted to forgoe all his power and become human, he could just will it so.
He won’t do this because he knows what happens to humans after death! [hahaha] 
Plus he’s no fool. Easily defeated, but no fool.
He became mortal, but took on the appearance of that of Humans.
Regarding willing things out of existence; that seems to be an ability exclusive to beings of god-like powers, such as a Nephalem at the peak of their power. I don’t believe the prime evils (probably with the exception of Diablo once he contained all 7 evils within himself), or the angels (probably with the exception of Inarius while empowered by the worldstone and Malthael after his attunement with death and absorbing the essence of the lords of hell) possessed the power to will things out of existence.
Of course, that is merely speculations on my part.
Guys, your comments are the best. haha
But the focus is this: Like Tyrael, if Diablo had its power (essence, evil) withdrawn (voluntarily or not), would it become a mere mortal?
I believe so.
I believe that the will and the power are different things, the will is the conscience of Diablo, and this can be separated from power, just as it happened with Tyrael.
Tyrael became flesh and blood after giving up its powers, before it was just energy, just like Diablo is today.
In the case of Tyrael, when separated, the divine power (grace, well) is in his armor and sword, in the case of Diablo would it be in the skull? (as shown in the video “By Three They Come”).
I believe so.
The materialization of Diablo’s power (which is not to be confused with his will) is in the skull.
Lore master, please do not take this the wrong way, but I love you right now. 
So many people do not know anything about the lore in the game they play, all they want to do is move fast and kill things. This is why I mostly run solo, I take my time and check everything out. If you are into the lore Nineball at Westmarch Workshop would be a good source, the guy is a Diablo lore encyclopedia. Keep the posts coming, I love the history lesson. 
Lilith seemed to will dead things back to life and she and Inarius created the world stone and Sanctuary from nothing. I know it hasn’t been explicitly said but I would assume they could, but it would take immense willpower and emotion to do so it is not something that can be done as easily as walking.
It could also have been a onetime mcguffin used in the novel to make a point.
Based on what’s been shown and told to us thus far, I don’t believe that is possible. The energies of angels and demons aren’t neutral and are in fact based on said being. As such, unless you can siphon and contain said essence into a device capable of withstanding its energies; the essence would start to have an effect on its area.
Examples of demons and angels losing or parting some of their essences while their bodies still existed or in process of restoration:
- Baal’s soulstone in Diablo 2. While Baal had no contact with the soulstone, it was still ravaging Marius’s body due to it being filled with Baal’s detructive essence.
- Tyrael’s sword imbued the Human Jacob Staalek with righteous strength
- Tyrael falling into Sanctuary during Diablo 3. His impact with the ground had some of his essence leave his body, which in turn caused the undead (including King Leoric, the Skeleton King) to rise once again.
If you take Diablo’s essence (which is in fact his energy) from him and place it. You would more than likely have undead risen and demons born from it in due time. Diablo (as well as the other evils) essence is just that malevolent.
Tyrael’s body still possessed this energy (essence). Actually, a better way of saying it is that, Tyrael is the essence. He can never truly get rid of it, not unless he dies, in which case he would simply be reborn or replaced.
That said, shedding his wings did remove a significant amount of his essence, a reason as to why he’s considerably weaker than when he had his wings.
Long story short: Tyrael, even while mortal, still is an angel and still possesses his angelic essence, and should he die while mortal, his essence would merely revive him or replace him in due time. The near same can be said about Diablo.
For most of the games that I’ve played, the lore is an important aspect for me. The Diablo franchise itself is one of the few that I’m heavily engrossed in. And honestly, I enjoy discussing Diablo lore whenever I get the chance (probably to the point where I may seem to be obnoxious).
The Worldstone had always existed, it’s one of the primary reasons as to why Heaven and Hell waged their Eternal Conflict. Lilith and Inarius (along with a number of other angels and demons) merely stole it away. They used the Worldstone’s power to create Sanctuary as well as hide it from Heaven and Hell.
I think I should ask Nineball to have you on Westmarch Workshop, the two of you could talk Diablo lore for 2 hours. The episode would be great. I enjoyed the Diablo 4 world and lore panel at Blizzcon.
The thread got my attention, a bit unusual nonetheless.
What do we know about Demons & Angels coming down to Sanctuary?
Angels, with a short duration, can come back and forth and Demons have to possess a mortal in order to manifest themselves.
From here I would say that it’s a matter of tuning, Angels & Demons can no longer walk free on Sanctuary like they did since Inarius changed the Worldstone’s tuning.
But what to say about Tyrael becoming a mortal?
I say that he tuned his essence toward Sanctuary and in the process his essence is occurring or is found at intervals and various locations rather than all together, mortal body, weapon, armor, … but destroying all of it would only made him back into the Angel he was.
Diablo becoming mortal, like said previously what would be the point? Unless he have the intention to die and see his essence going exactly where the Angel of Wisdom is, to take him down and grab the souls for an unknown vile project.
It’s a question with which it’s difficult to don’t speculate.