Speaking of Deus,
Going too deep into his combat abilities is a bit premature because the circumstances were special. I think most of the community agrees that his performance against possessed MC was overwhelming due to the short time that MC had his new powers. Of course that could be wrong and Deus could be a level 6 or something, but w/e.
I compiled a bunch of quotes that showcase his unique insight, his differences with Zack and some oddities that seem to fly under the radar in his fight against MC.
1)
Dexter "You've become too reliant on Deus. He is no replacement for Zack."
Xanthe "On the contrary, he is even more precise."
Both Zack and Deus are level 4 at the beginning of the game. I think it's a fair assumption to say that Zack is older than Deus, which should make him more powerful. But Xanthe says that Deus is more precise.
I think the reason for this is how they interact with time. Perhaps Zack has better "future sight" but he can see more general things, while Deus can follow certain branching time points and precisely find out what is going to happen, but he is more limited at how far he can see in the future.
2)
Deus "As I recall her name is Ella."
You "(Ella?! She's here? And he knows her?)"
You "So... Ella's with you?"
Deus "Hmhmhm, no, quite the opposite."
You "Then... you're enemies?"
Deus "Of a sort."
You "Then shouldn't you go... I don't know, capture her, or something?"
Deus "My venerable leader would certainly think so. Malik has wanted to end her rampage for some time now."
Deus "However, I'm going to need her work completed if this whole mess is going to be sorted."
You "(....Who the fuck is Malik? And why is this guy talking like he knows me?)"
Deus "But that brings me to you. You in particular should be careful of her [name]."
Deus "Your future with her is murky, you'll want to be prepared."
Now this piece of dialogue is especially interesting for 3 reasons.
First it shows that Deus has a plan that is seperate from the rest of HERO and it's quite possible that he hasn't informed them of it at all. Which makes him a rogue agent for all intends and purposes.
The second interesting piece is that he can't see MC's future with her. That seems like foreshadowing, that MC will get to make a choice with Ella in the future.
The third is that whatever Deus knows, Zack seems to not know. While Zack is injured, he should have been at least as powerful as Deus was. While we don't know when Zack got injured, Ella's schemes are not new and it seems to me that Zack hasn't got a single clue about what is going on.
3)
Deus "You don't want to face her until you're strong enough to impress. And even then, you'll want to keep your secrets close."
Deus "Those eyes of hers see a lot, but she doesn't have the understanding you do."
Deus doesn't know who Ella or MC are. Additionally MC doesn't have any understanding at all. Not of the situation he is in, not of what it's expected of him. The only thing he seems to understand very well is his powers.
For Deus to say such a thing, and considering how deep he has put himself in this situation (meaning that he wants to see it to it's end), it means that not only he can see the future, but he can get very specific details. He seems to know exactly why the MC is needed, despite the MC not being anywhere close to the level that he should be.
4)
Lucius "But there'll be more fear. I agree with Malik, better we just deny everything and have Zack and Henri cover everything up like the old days, they'll be suspicious but there's not a whole lot they can do about it."
I may be overreaching here, but I think Deus requires a more controlled environment, while Zack can predict and alter without much hassle. Any operation of the kind that Lucius describe would be huge in scope, considering that Henri's powers seem poorly suited for precision attacks based on what Xanthe says.
When Zack says that he can't contribute, the easiest thing to do is to just switch out Zack for Deus, but Lucius doesn't do that, he just surrenders his idea.
5)
Deus "To think the it would split in a direction like this. Did I make a mistake? Or was it you... There's just too much for me to tell."
Deus "No matter. I can kill you, even from here, as long as I keep my eyes focused on this point. Then things will right themselves."
Deus "It's for you own good, believe me. I'll put you out of all our misery."
There are a lot of things going on here.
First, it shows that his powers are probabilistic and not deterministic. We can't know how it works for Zack, but Deus seems to "explore" the future, not see it. Which could also explain his night terrors, seeing all possible futures and some of them being too hard on the mind.
Second, considering that Deus wants Ella's plan completed and has claimed that MC has unique understanding, making sure to protect him during all this time, he claims that things will "right" themselves. Is that a fourth wall thing? Is Deus Weirdworld sending us to main menu and forcing us to reload? Or it's just that MC is just one candidate and there will be others if Deus manages to kill him now.
Lastly, he claims that he kills MC for his own good. That's a bit cynical unless he knows that MC is trapped in the consciousness of this thing and wants to spare him the torment. Of course that would contradict MC getting embraced by the entity in the darkness but we can't possibly know the particulars.
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At last though, I'm not sure what to make of these. Hopefully someone will find them useful and give me more ideas.