In a bad end with Ella it's confirmed that you inherited the traits from _both_ the third and the fourth however, meaning that yes you are the descendant of both, the choice in the beginning being the main one. So yes as stated his specialty is both transformation and memory, he just hasn't trained the memory part of his powers nearly as much as he has the transformations.
Edit: To elaborate a little more, something capable of brushing off a numbered and causing Ella, who's normally flippant towards everything, to stand there shaking in fear, showed up purely because you were there. If you only had the transformation specialty this would not have happened.
In my headcanon this could be because those two traits in combination with each other could be capable of replicating every other trait, provided you either consume/properly dive into someones memories/dna to be able to copy the functions that cause the powers to manifest. Like a combination of Sylar and whathisface from Hero. Personally I have a hard time seeing what else could cause something that seems to be above the numbered to care otherwise.
For me, it's the opposite. The Dark Glowing Eye Monster was there for the 4th. My thoughts on it is it's the Dark God/King lesser form. It's the main part that remained after the Numbered split from it. To regain it's full power, it most likely needs to consume the Numbered as they represent "parts" of itself and the power it originally owned. It only seems to manifest when a Numbered is involved, as you can see from the 4th and Valravn popping a boner when the 2nd arrived.
Valravn statements are really important for this because he's assumed to be a spawn of said monster. Him calling Mommy "The Memory" and the 3rd "The Body" seem to line up with the thinking. He also sees the 2nd as his enermy and that his prayers can now be answered as he flys out looking for his king(?) after the 2nd arrived.
This also leads to one of the reasons why the Numbered don't stay on this plane for too long. The Dark Monster might only be able to reach them while they're not in their own plane/realm. You might be wondering why it didn't attack them in the beginning then? The simple answer is that the 3rd and 4th together would be too much for it, currently. When Mommy stayed for too long, by herself, it ate her. When the 2nd manifested, Valravn quickly left to look around because the 2nd wouldn't stay for long. This indicates that his king, if it's the Dark Monster, is only interested in showing up when it's a Numbered.
There's also Xanthe. He hints that Tiffany's monster may have been one of the 12 Numbered(7th - 12th) and stated that said monster corpse was a "part" of a greater monster originally, made from it's own body. Which would circle back to the Numbered's name actually representing the part that split from the monster. If Tiff's monster is a deceased numbered.
Of the current Numbered, we know that:
The 1st represents "The Authority"
The 2nd represents "The Power"(?)
The 3rd represents "The Body"
The 4th represents "The Memory"
From all of this, we can then draw the conclusion that it wasn't there for the MC but for the 4th, which it consumed. It only killed the MC, and likely Ella, because they're direct spawns of the 3rd and 4th. If we follow this line of thinking then the MC was just unlucky to be there. If it wanted the MC, specifically, it had ample opportunities to get him over the course of the game. The 4th though? She rarely appears and when she did, alone, it came for her. Of these 2, only one of them are hard to get and they so happened to kill and consume that one immediately.
As for the MC's power. It is minuscule compared to this Dark Monster's assumed original power. Especially so when you realize that it had both the 3rd and 4th's power as it's own originally. Even the MC's hypothetical full potential wouldn't hold a candle to a being that all of monster powers originated from in the first place.
That's it, that's the theory, for the most part. There's more to it but I just put the more straightforward stuff down. It's mostly from all of the info currently in the game. If you're curious about where these are all stated at, I'll list them for you here:
- The Dead End with Ella and the 4th for the Dark Monster appearance, obviously. Though you can see it in the MC's dream after he reached lvl 2. A detail that's actually interesting because he never saw it and it scared him more than the other monsters.
- For the Xanthe's part, it's when Tiff gets turned into a Superhuman.
- Most of Valravn scenes have info so I'd suggest just reading all of them. That includes the flashback during the MC's fight where you see Valravn getting turned by the Dark Monster(notice it's hand is the same that killed the 4th on that dead end).
- For the Numbered's naming, you'll have to do a playthrough for the 3rd to see Valravn calling it "The Body" and learning that it struggled with the MC at the beginning. You'll also learn that Ella is a spawn of it.
- For the 1st being called "The Authority", you'll see that after Ella and Jake escape HERO Base. I also advise seeing Jake's death scene as you get to see the 1st in it's plane before the 3rd and 4th attack it.
Also, I can't stress this enough. It's just a theory. It's all still a mystery, especially for this Numbered stuff. I do believe Valravn's card may have the important pieces of information that could bring us closer to the truth though. If we ever get that here or it's told in game, we should be closer to the answer.
I think you have some things off.
1. WW has said there's no effect on the story for what monster you pick, but not that they're identical. They are explicitly two different beings with different names, numbers, and powers, one of them being the 3rd (Body) and the other being the 4th (Memory) (I might have these backwards, but fuck it). Like, I doubt two of the remaining 6 apostles would just be the same thing.
You're right about the 3rd and 4th. The Dev has already shown the difference between the 2 in game. Even the opening at the start shows a clear difference. A difference that gets expanded on later depending on who you chose. Only way you wouldn't notice these 2 are different being is if you only did one playthrough.
If you chose the 3rd, who's called "The Body", it struggles to read through the MC's memories and decides to use it's tentacles on his brain directly.
If you chose Mommy 4th, who's called "The Memory", she looks through the MC's everything without touching him at all. A detail the MC notes later, by the way.
At most, the 3rd and 4th are twins, beings that came into existence at the same time together. Maybe even originally one singular being that split again after the original split. They share the same abilities but it's clear by their name and what they've shown, that they specialize in their fields.
That ends my wall of text, for today.
