*spoilers, you have been warned*
After seeing the cutscenes for VD, I gotta admit that I was really disappointed in the actual story on Vergil's downfall for gaining his power.
1) Where was he transported to? You'd think he would be transported in Limbo, but Limbo has already been collasped into the real world. So my only guess that he's in some form of Hell seeing how Eva is also there as well. (Which imo, doesn't make any sense).
2) How did killing hollow Dante, hollow Kat, and himself in his hollow form, unlock his true power? Most importantly, where did these hollow forms even come from? And why was hollow Vergil helping him out in the first place? And didn't Vergil already unlock his Doppelganger against Dante? Yet you gain this skill after Vergil defeats his hollow form and unlocks his "true power".
I don't get it at all. It sounds like the devs just threw this together for the sake of Vergil's story.
3) After gaining this new-found power . . . he becomes powerful enough to control demons?
....
Why?
What I got from it (elaborate theory ahead, folks): I'm willing to bet the entirety of the DLC takes place in Vergil's mind. He uses the portal to get to mother's grave and collapses on it on the verge of death. And then he goes through a journey through his own soul. You remember that place with the giant statue in chains that Dante "went" to whenever he gained a new Nephilim power, and once he finally unlocked his trigger, he stopped going there? Vergil spends the entire DLC in a severely twisted version of that place, falling apart because he's losing his mind. It looks like Hell because it's a reflection of his pain, both physical and mental (represented by the beating heart, wounded in real life and wounded metaphorically by Dante's betrayal). He probably already went through it one time before just like Dante did, and is forced to go through it again because he's dying and his body is restructuring itself. (Sort of harkening back to DMC!Dante needing to basically die and resurrect to unlock his trigger).
Dante and Kat are just hallucinations, reflections of Vergil's own insecurities that he has to defeat to gain confidence in himself again. He could have confronted his doubts and reached positive self-realization and increased his power that way (like Dante did), but chose instead to crawl deeper into his own rage, resentment, and delusion, which Hollow!Vergil kept feeding to him, because hollow!Vergil represents everything Vergil thinks he needs to become (actually, it's everything Vergil needs to overcome, but that's where Vergil goes terribly wrong.)
As for Eva, remember when Dante spoke to her spirit in DmC, and she left him once he achieved his full potential? Apparently, like in the original DMC, her soul is tied to the amulets. Eva's not a hallucination, and she's not trapped in Limbo or Hell, she's trapped in Vergil's own internal madness, and she can't be free until HE'S free, because he's using HER amulet to attain this power of his. And she can't reach him anymore, so her spirit's stuck in the depths of his insanity until he's not Hannibal Lector anymore.
So when Vergil wakes up at the end, in the real world, he's healed himself and he has an even better grasp on his power than he did before; he's given in to his demon side entirely and all the power associated with it (unlike Dante, who was still fighting against it at the end of DmC). And the demons, masterless, trapped in the human world, and looking for someone with the power to lead them, recognize that in him immediately. So he becomes their new boss.
(And Dante is an idiot who could have avoided this whole mess with a little diplomacy and maybe not trying to murder his brother, but noooo. So now Vergil's a crazy demon messiah twice as powerful as he was before and he's gathering an army that's going to smear Dante all over the sidewalk like a dung beetle.)
I liked it a lot, actually. It demonstrated metaphor and the hero's struggle a lot better than DmC did, though it could have been more complex (seriously, Vergil, your mother's "favorite"? Really? Are you twelve?) It also made me sympathize with the main character more. Vergil's a twit, but it's shown to us why he's so messed up in the head, and also why it's his own damn fault, so I felt bad for him without feeling he was justified. Never got that sense of flawed humanity with Dante.
But that Super Saiyan hair was stupid. So stupid. He looked like a troll doll.