Cdtrjyty

I am playing the Old Gods DLC, started in the north as a Pomeranian duke, formed the Wendish Empire and have now reconquered much of the Byzantine Empire, whose title I have usurped. I stayed as a (reformed) pagan. I seem to remember that the Byzantine Emperor has two unique decisions available: mend the schism and restore the Roman Empire. Being a pagan, it makes perfect sense that mend the schism is not available to me. However, I would have expected the Restore the Roman Empire decisions to be available. To clarify, I am not saying the decision is greyed out, it is not listed as a possible decision at all.

Are there some conditions I must fulfill before the decision will appear as an option (even if greyed out)? It would be great to know the exact list of conditions.

You have to be emperor of Byzantium and be Christian for the decision to restore the Roman Empire to show up. From decisions/realm_decisions.txt:

restore_roman_empire = {

    [...]

    potential = {

        has_dlc = "Legacy of Rome"

        age = 16

        prisoner = no

        NOT = { trait = incapable }

        has_landed_title = e_byzantium

        religion_group = christian

    }

    [...]

}

If you don't like that, you can simply remove or comment out the religion_group line.

To restore the Roman Empire you must control Rome and its former territory. That means taking over Italy and the Holy Land. Until you control the old Roman Empire, you won't have the option to restore it.

As of the release of Holy Fury, you can now restore the Roman Empire as both an unreformed and reformed Hellenic.