I highly doubt that they will give Hakunon such a prominent role as the master of Nero. Nero's partner has to be Hakuno. Personally I think her Servant will be ether Tamamo or Nameless.
With that said, the choice of words here is rather interesting. I think that Oblitus should be the first half, showing the fall of our heroes (this is where the ruins of Domus Aurea could be coming from) and Illustrius should be the second half, showing their triumph.