What do you think of theories Diavolo is really evil and killed Lilith?
The Theory of Evil Diavolo
There are a few "Diavolo is evil" theories going around, beyond the fact demons are evil that is, so let's take a look!
(For Diavolo Romance theory see Further Reading at the bottom ^^)
Firstly, the idea Diavolo orchestrated an entire plot that necessitated killing Lilith to secure Lucifer's loyalty...
I think it really depends on what level the game storytelling is operating, and as I've mentioned before, the plot of gacha games is unlikely to have huge radical shifts that change the status (or relative good/evilness) of characters due to needing consistent promo.
So while I think from a story point of view it's an interesting headcanon, I don't think there's enough there for it to be an actual workable theory.
For one thing, it requires us having either sorely overestimated Lucifer's intelligence, or underestimated his own lack of care and concern for his own family.
We know that the latter certainly isn't true, from what he went through trying to protect Belphie, and previously from protecting Lilith from being discovered in her human form. If Lucifer had sensed a plot from Diavolo that would harm his brothers or relied on them being manipulated, he would not have made them collateral damage to saving his sister.
As for Lucifer's intelligence, I think he is well aware of how things work in both the Devildom and Celestial Realm. Where he struggles is with emotional communication, but he's still savvy enough to recognise when Diavolo is acting odd or distant.
I actually think there is one main reason Diavolo sought the loyalty of Lucifer and thus the loyalty of all seven fallen angels - Lucifer's power is a rival to Diavolo's own power.
We tend to assume that being the demon king-to-be, Diavolo is the most powerful demon. But we are shown zero evidence of this, beyond his ability to have Lilith reborn as a human.
However. We do know that Barbatos holds tremendous power over time and reality, meaning it is far more plausible that it was him who had Lilith reborn, not Diavolo.
And we also have plenty of examples of Lucifer's power, bearing in mind that we only ever see him when he's struggling not to lose control. His power is so great he can make even a fake version of the mighty Cerberus obey his command, and he has a mastery of (and resistance to) magic that so far has no limit.
Despite their frequent arguments, we also know that the brothers are loyal to Lucifer - they followed him from heaven into hell after all, and even Satan who did not, and who has the greatest reason to hate Lucifer, still chooses to stay as part of his family.
All that being said, my own thoughts are that Diavolo is likely to be working towards a greater good, as he has been shown to be saying over the centuries.
His aim is to unite the three realms, and he appears to be following some kind of strategy to do. He had already met with Lucifer before he fell, and I don't think it was Diavolo who planted the angel's doubts - I think he merely recognised Lucifer was already doubting.
A war in heaven was thus inevitable, though the death of Lilith unexpected. But it afforded Diavolo the opportunity to gain Lucifer as a definite ally, rather than a powerful potential rival.
RAD too was already in operation when Lucifer visited as an archangel, the intention of the visit was apparently for Diavolo to show off the Academy.
RAD is named after Diavolo, meaning it is certainly his venture, and the demons are taught everything from maths to curses and potions. But there is no end goal of graduation, it is a constant place of ongoing education and, imo, rehabilitation.
The brothers reminisce that not long after they first fell, they had to kill many succubi. But there is no sign in the present Devildom of any such clashes - even the Little D's, the lowest of the lesser demons, whiz about doing as they are asked.
RAD exists to keep demons focused and prevent them being, well, demonic.
This makes for a more efficient kingdom for Diavolo, but also for a realm in a better position to argue for peace with the Celestial Realm.
But why the need to strive for peace, when there's no sign of there having been a war?
The war in heaven was down to, at least, the seven fallen angel brothers. There were no demons involved.
Yet Diavolo says to the Archangel Lucifer, that without working together, all three realms will face ruination.
This is a warning that should be taken seriously, given that Diavolo's butler demon just so happens to be able to see every potential future.
If Barbatos has seen that the majority of futures end in the complete annihilation of the Devildom or of all three realms, then Diavolo would have to enact a grand plan to try and shift them closer to the few realities in which that doesn't happen.
And I would imagine that the further into the future Barbatos looks, the less stable the results. So Diavolo is flinging absolutely everything at the wall to try and unite not only the Devildom with the Celestial Realm, but with the human realm too.
But. As I said, Diavolo is working towards a greater good. But that doesn't mean he is working towards what is good for the characters we know. In fact, that kind of goal tends to rack up the collateral damage with little remorse.
The reason I believe our characters will be safe, is down to the gacha game reasoning mentioned before.
Could Barbatos Kill Lilith/MC?
This is the other main theory I've seen going around, that Lucifer's obedience will be forced as otherwise Barbatos threatens to go back in time and undo Lilith's rebirth as a human, thus extinguishing the life and existence of MC.
There are three main problems with this.
Firstly, even in the convoluted time travel that OM has, to go back thousands of years and wipe out an entire bloodline, would change ALL history from that point. Including that of the Devildom. Lucifer would not have had to swear allegiance to Diavolo, and torn apart by wrath he may well have overthrown the Prince and reigned in hell - as our more familiar mythology plays out.
Even if Barbatos managed to find a current reality in which Diavolo still lived, his entire plan to have peace between the realms would be destroyed, as the other two realms could well be totally different.
A change in time so far in the past is madness.
Secondly, because this would break Lucifer's obedience completely. Regardless of what Lucifer chose, Diavolo would have made enemies of the seven brothers and lost his powerful allies. Lucifer might obey the order that saves MC, but Diavolo would be set on the path of extinction.
Thirdly, it positions either Diavolo, Barbatos, or both as undoubtedly evil characters. We have been given an entire cast of mostly grey characters when it comes to their moral compass. An angel acts like a tyrant. A demon acts like a guardian angel. A butler appears suspicious. A famous sorcerer is both a help and hindrance. And so on.
This makes the game hugely marketable due to diverse appeal - nobody's favourite character is irredeemable, even the one that killed MC!
To turn from that and make one character irredeemable this far into the game, is frankly not a very smart PR move. You'll get a lot of backlash, and it turns previous interactions with said character far more sinister than was probably ever intended.
Eg, see how Diavolo reacts like a fangirl around Lucifer in the Butler event, blushing and pouting that he wishes he could have Lucifer as a servant. Now picture that scene knowing Diavolo killed Lilith to get Lucifer's obedience. Or picture that as the same Diavolo who will threaten to wipe both Lilith and MC from existence.
I mean unless they mean him to be a total creepy creep it really doesn't work!
Barbatos as Lilith's Lover
And the secondary theory that's been around for a while, which unlike the other two I'm not gonna rule out 👀
Did Barbatos then choose MC as exchange student? Is he in reality the human that Lilith fell for in the first place, reborn as a demon?
To the first question, no. If anyone "chose" MC by putting their application in the right place when Lucifer opened the window, I would lay bets on that being Lilith, the resident spirit of the House of Lamentation who has been watching over them for centuries.
Or it may simply be some kind of latent angel magic recognising a fellow former-angel, bringing paper and demon together.
Diavolo encourages the selection, which makes me wonder if it is indeed down to Lilith. He may not know the spirit is there, but he will surely recognise when something appears to be "fate" and he does in fact say as much.
As to the second question, this stems from one of Levi's incredibly long anime titles: I Fell in Love with an Angel, and I Know It Was Fate, so I Tried to Get into Heaven, but Messed Up and Was Reborn as the Demon Lord's Manservant... So Please, Just Hear Me Out!
And the sequel: I Actually Got Used to Working as the Demon Lord's Manservant and Have Started to Really Enjoy My Life in the Devildom, but now a Succubus who Claims to Be the Reincarnation of My Long-Lost Sister Has Shown Up, as Well as an Angel Claiming to Have Been My Childhood Friend Reborn (Who Was a Total Tsundere, by the way) and Honestly I'm Not Sure Whether This is a Good Thing or a Bad Thing at This Point.
Those are long titles 😭 Anyway, we already know that in-world fiction can reflect the actual storyline of the game, as seen with TSL. Even The Magical Ruri Hanai: Demon Girl stars a character who has powers in the Devildom but appears to be just a mere human in the human realm, rather like a certain MC...
In the case of these titles, the only "manservant" we know of is Barbatos, as Diavolo's butler. He was already a demon before Lilith fell, as seen when Archangel Lucifer visits the Devildom.
However, this is also Barbatos we're talking about, a demon with the ability to move through time. And traditionally, Barbatos is both a demon and a fallen angel, which might perhaps describe someone who attempted to become an angel yet became a demon instead.
In fact, given that Barbatos is probably far older even than Diavolo, it may well be that he could have been reborn many times, for some greater purpose or pure shits and giggles. Lilith only recalled her previous life as an angel when she died as a human, and living many lives would be a good way for a time lord demon to gain knowledge, then move to the Devildom so he never bumps into himself. One such Barbatos could have fallen in love with Lilith.
Following this theory things get a little confusing, as nobody really fits the long-lost sister succubus role (including MC) while the tsundere friend as angel would be... Luke??
I can't completely rule it out, mostly because we do know that via TSL, Simeon does seem to be some kind of prophet (especially if his play turns out to do similar) but there's little proof thus far that other fictional in-game media is similarly linked to the game plot.
And while it's sort of plausible, it's way over complicated and probably just a throwaway gag at very long titles.
Barbatos' input extends to his ability, imo, to have Lilith reborn, and for his loyalty to Diavolo. The butler refers to Diavolo as young master, which suggests he perhaps served the demon king before him, or at the very least that he is far older than the Prince.
Thus it could be that Barbatos is not exactly loyal to Diavolo, insomuch as he is dedicated to keeping the three realms from upcoming ruination. Diavolo is perhaps the best suited to make this plan happen, as leader of one of the three realms. And arguably, leader of the most straightforward realm.
As a wise lobster once said, the human world is a mess.
And we know that Lucifer's greatest fear is dying and his soul ending up in the Celestial Realm. But it isn't just Lucifer who thinks little of his former home. When Lilith tries to save her human lover with the forbidden fruit, she could have instead let him die, and then reunited with him in the Celestial Realm.
But instead we know that she loved the human realm best (as did Belphie), and so she took the larger risk to save him, instead of losing her connection to the human realm.
When MC visits the Celestial Realm we see one outside shot, and one room. Unlike the Devildom where we are shown around, and introduced to various characters, the Celestial Realm is barren and empty. Soulless, one might say...
Simeon has visited the Devildom before. And Luke, Michael's biggest fanboy, how happily bakes cakes with Barbatos, one of the most powerful demons and beings in existence.
Just how heavenly is the Celestial Realm 👀
But Lucifer Might Be An Angel!
I've kinda addressed this elsewhere, but the short version is this - a demon being nice is not the same as an angel. Like, that's not the defining factor.
Lucifer and his brothers became demons because they fell from heaven. And they fell because they disobeyed and rebelled. Just as Lilith was falling because they were trying to save her from being obliterated by god.
If the bar was set by good vs bad deeds, or selfless vs selfish deeds, Luke and Simeon would both have turned into demons by now. One is full of wrath and pride, while the other spends his time writing trashy books and an anime series under a penname that seems to require him having stalked a bunch of demons.
The demon brothers do not want to be angels. As demons they are free, have evolved, and most importantly of all - have not and will not forgive their father for his murderous wrath.
Also, it doesn't make game sense, as previously mentioned.
Additionally, when Barbatos says the old Lucifer would never have not been on Diavolo's side, he is incorrect. Quite why he says this then, is unknown, other than perhaps to give Lucifer a warning of some kind, and to push everyone towards the resolution that is best for the Devildom and, hopefully, best for our characters.
(See also the earlier screenshot of Diavolo saying he believes everything happens as it is meant to, which would include MC's closeness with the demon brothers.)
tl;dr I don't think Diavolo is evil, but I do think his jealousy is a precursor to secondary characters becoming romanceable.
What we may well see is our characters being led to believe there is a nefarious plot. Here's hoping they don't leave us on a cliffhanger 😭
Personally, I find Barbatos and Simeon the most suspicious characters, but again, they are unlikely to be evil.
And the one thing about Diavolo that does raise my suspicions is the where, when and why of the sleeping demon king 👀
Lesson 28+ Facts and My Theory
Diavolo and MC (spoilers Lesson 28)
Obey Me: The Theory of Time Travel
