You're confusing me. Do you want a dual hero? Like two people becoming the same hero in the same world in the same time frame? Or do you want a split hero? Where two separate people become the same hero in a different world/time line/whatever in the same time frame?
As for your Dragon Break bit: Could he? Yes. It'd more or less apply only to the Mundus, but he could. Would he? Unless you gave a good enough reason (or purposefully ignored it like I suggested above), no he wouldn't. Doing something like that invites too much Chaos/Padomay/whatever you want to call it into the system, his system. One where he is an Anuic being. Especially since splitting time in two essentially means dividing himself in half. Also, there'd be other... unintended side-effects. But hey! You've got a convenient explanation for skill/magic changes.
The latter,
Mehrunes Dagon, definitely the latter. I want a split hero where two separate people become the same hero in a different world/time at the same time frame. The question is making it work while being lore correct. This is how I can explain why my friend and I can play the same games as two different players and yet have the players be companions of one another at the same time. Juliana (my friends PC) would play the game with Vedaa (my PC) as her companion here and there. Not all the time, but like, once in a while, they would run into each other, only the other wouldn't be doing the main quest. But on the other side, it'd be the opposite. It's kinda like the IS and IS NOT in a sense.
I guess it would invite a lot of chaos if the oblivion realm were doubled,
Mehrunes Dagon. I mean, Oblivion would have to be doubled because the CoC goes to it in TES IV.
Perhaps
Juliana and
Vedaa (my friend's character and my character, respectively) could be doppelg?ngers. Naa, that's not what I want, though. They're not the same person that is simply split. Juliana and Vedaa are completely different people. They were both created by the Aedra with the help and ideas from the Daedra (mostly due to being tricked into allowing the daedra to help them). Juliana was made first by Julianos and Boethia, with the mixture of powers from a few other daedra, which is what makes Juliana such a powerful, yet sharp and keen heroine in the TES series. Vedaa was created in TESIII Morrowind by Dibella and Mara, with help from Azura and other daedra who probably should not have been involved, like Sheogorath and Clavicus Vile, etc... Both Vedaa and Juliana are dark elves. Juliana is not all good nor all bad, and neither is Vedaa. Juliana becomes the master in all the guilds (thieves, fighters, mages, dark brotherhood, etc...) due to her diverse personality and skills.
Vedaa, on the other hand, because of the mix of conflicting daedra and aedra, is somewhat bipolar and not as wise or talented as Juliana, yet she does have a superfluous amount of magicka and such. She doesn't have the desire to join all the guilds, though, like her counterpart. Vedaa is also much more immature than Juliana.
Why this subject is hard for me to come to a conclusion is because they're not opposites, as far as being mortals. It's more of like, what Juliana and Vedaa represent are opposites. Juliana was basically created in the 2nd era by Julianos to defeat Tiber Septim because he was going to conquer all of Tamriel with the Numidium. The aedra didn't like the idea that a mortal was going to destroy the very realm that the aedra had sacrificed themselves to create. It's like building a playhouse for your kids and then they get their baseball bats and start tearing it apart. The parents would be furious. And so too are the aedra over what was going on. So Juliana was created to stop this. But she was killed by Numidium and Tiber Septim (General Talos) conquered Tamriel. Blah blah blah.... Juliana is created again in the time of TESII: Daggerfall because this is the reawakening of the Numidium and the aedra don't want to see another catastrophe happen again by it. So Juliana is remade(reincarnated) and solves the main quest, etc... I guess they might have preserved her dreamsleeve soul for later use.
TESIII: Morrowind - Juliana is not all good since she assassinates & steals, but her path is directed towards doing what is right. She was originally Julianos's idea, and with the influence and convincing by Boethia, she was made in the 2nd era and once again in the 3rd era. Okay, so now onto how
Vedaa enters this story.....
The daedra, like little kids wanting to drive their dad's car, want to create a mortal of their own design. Of course, the parents (aedra) know that if they let the kids (daedra) drive the car all by themselves (influence all the attributes and representations of a custom mortal), that they'll get in a wreck (that the mortal will be completely obscure and contradictory and cause far more problems in the mundus than solve.
After the hero of Daggerfall (Juliana) solved the numidium quest, etc... Arkay suggested to his father, a few years down the road, that Juliana would also be perfect to be the reincarnation of Nerevar, a prophecy told to the aedra by the Queen of Dawn and Dusk. Azura didn't see Juliana as such, though. She gossiped with her friends Mephala and Boethia about how the idea she had concocted centuries ago to reincarnate Nerevar and destroy Dagoth Ur, etc... was being stolen from her by the aedra. "It was my idea to reincarnate Nerevar to end the blight and stop Dagoth Ur. And those infernal Aedra are cheating me out of my prophecy by using this mortal whom I know isn't right for Nerevar's incarnation!" Boethia and Mephala agree with the irate daedric prince.
Sheogorath, Sanguine, Vaermina, Clavicus Vile, Mehrunes Dagon and Nocturnal are eves dropping like little kids listening to their other siblings fight on the other side of the door. They later get together and conclude that they(daedra) deserve to shine for once in the mortal realm through a creation of their own. But they don't want to sacrifice themselves. Vaermina suggests that Boethia trick Julianos again into creating another mortal, except allowing the daedra to influence what and how the incarnation is made. Boethia had very little influence on how Juliana was created (both times). His influence of assassination and plot were used, but other than that, she was purely all aedra
(Juliana is basically an aedric construct). Boethia declined and said that Julianos would be too suspicious and not go for it. "However...." said the dunmer god, "Mara is a real sweatheart.... as well as a real svcker. I can deceive her into helping us."
And so, Boethia, prince of deceit and conspiracy, makes an offer to Mara, who at that time, is conversing with Dibella. He tells Mara that he and the daedra want to create their own mortal who will be loved by all and bring compassion and peace to the Mundus. "Your (aedric) created mortal subdued war and hostility but did not bring peace. Azura, Mephala and I know that your mortal will not be the incarnation that Azura had prophesized. She(Juliana) may defeat Dagoth Ur but she will not bring peace to the mortal planet. We(daedra), on the other hand, with our powers, can. We simply lack the capacity and the will to endure the process of creation. Will you please help us? Help us help you, Mara. If you will, don't tell the other aedra, especially Akatosh, for he has never looked too kindly upon our ideas or concepts."
With that, Mara, as well as Dibella, were convinced. In 3E 410, the two aedra congregated in Oblivion and secretly devised the creation of the new incarnate, another female dark elf. Most of the influence of the incarnate's personifications were the product of Azura and Boethia. Dibella and Mara were tricked, but were not ignorant. With a gathering of almost 10 daedra at this event, the goddesses wouldn't let them infuse the mortal with
all of their powers..... only a little. But a little bit of magic from 10 different daedra goes a looooooooong way.
Thus, into this new mortal incarnation, the daedra poured their treachery, magic, ambition, uncertainty, hatred, love, kindness, insolence, light, darkness, debauchery, revelry, madness, control, wisdom..... in conjunction with the compassion & understanding of Mara and the artistry & aesthetic, yet erotic, beauty of Dibella. And out popped a dunmer baby girl into the mortal realm of Nirn.....
Vedaa.
Following the jolt of this creation, Akatosh and the other aedra were astonished and disappointed in what had transpired. After much arguing, Akatosh decided to let the new incarnate be. Dibella and Mara explained that this mortal was to be the true incarnate of the Nerevar who would bring peace to the mortal plane. Akatosh was not convinced. However, because of his high respect for Dibella and Mara, he allowed them to keep this mortal on Nirn, despite the superfluous daedric influence that went into the creation process.
On one condition though........ that Juliana, the Aedric creation
(with a tiny tint of Boethia), would also be the Nerevarine in addition to their daedric creation also being the Nerevarine. They all thought for a moment and finally agreed.
For this to work though, Akatosh did something he was not fond of doing. He summoned his greatest powers to allow time to be convoluted and the Aetherius to be doubled within its own creation; a doppelg?nger of it's own ethereal existence. (This would allow, for example, Azura to give both of the incarnates the Azura's star; to allow both incarnates to travel to Oblivion with the same affects happening, though by different characters at different times). The et-Ada as a collective whole, were not doubled.
Explanation: Think of the realm of Oblivion, which surrounds Mundus, as a basketball. And the basketball is doubled within itself in an alternate dimension. And time can be represented as a long piece of shoe string. Take the string and instead of having it wrap around the ball once, wrap it around twice. Through the eyes of the et-Ada, it's like wearing 3D glasses. When you close one eye, you see everything red; close the other, you see everything blue. Apply that to this. Close one eye, you see the mortal plane with Juliana as the Champion. Close the other eye and you see Vedaa as the Champion. Open both eyes and you see them together but not in the same dimension. The aurbis is still just one piece, but it's now split with an alternate doppelg?nger dimension. The reason why time has to be doubled, or wrapped twice, is, for example, when the Juliana does the quest for Azura and receives the Azura's Star, Juliana might have done that on the first Morndas of Rain's Hand. Vedaa, on the other hand, might have done the quest for Azura on the third Tirdas of Sun's Height. Both these two CoC's do the same quest and receive the same item.... but at different times. How it works is when Azura presents the CoC with the Star, by passing across two timelines, Azura can do one single action at one point in time on her side, but occurs at two different times in the mortal realm. Perhaps time should be doubled instead of wrapped twice. Same thing applies to seeing Sheogorath. He's just one entity, but he sees both Juliana and Vedaa at the exact same place, just at different times in their realm. But to him, he sees them both at the same time.
Is this making sense to you guys?
Mortazo, I'm super anol about being lore correct, if that answers your question.