Yo guys, I've had a theory for a little while on the identity of Urizen. I'm pretty confident in this theory, so if you want to avoid any kind of possible spoilers don't read this.
So, to figure out the identity of Urizen, we need to figure out the few things we can deduce about him.
1: He is being kept so secret for a reason. There is no reason for everything surrounding him to be so secretive if his identity is not important, therefore we can deduce that he is, in some way, quite important.
2: He is not Mundus. Developers already confirmed this, although admittedly it's possible they lied to keep it hidden. I'm doubtful about that though.
3: He has some kind of connection to Mundus. Despite not being Mundus himself, the aesthetic of three eyes in a triangle shape on a black, voidesque background is quite telling that he's supposed to have a connection. The only major difference is the colour.
4: He is more powerful than any other villain thus far. Showing that even Dante in his current state is not as powerful as Urizen means that he's possibly the greatest threat in the series thus far. In fact, I'd state this as evidence against the theory that Urizen is Vergil, since Vergil has never been even remotely as powerful as Dante's post DMC1 forms.
5: We have never seen them before. I also heard this stated by developers, but admittedly I can't remember exactly where I found it.
So in total, we have 5 major points. He is definitely someone important, it is not Mundus, we have never seen them before, but they clearly have a connection to Mundus and we have reason to believe that he is far more powerful than Mundus. What if... Urizen is Mundus' father?