Just as a recap, there are four hierarchies in the demonic level for demons, which start from Lower, Greater, King, and then Grand. Each has its tier, starting from 1st, the weakest, to the 7th, the strongest, depending on the number of demonic cores present.
Currently, Raph lived in a period where most nobles weren't even aware of the Gate openings and the invasion of demons, which occurred scarcely throughout the whole Continent, and this was because of the barrier separating the Demonic Realm and the Mortal Realm .
Though demons of the lesser hierarchy had the opportunity to make holes through it and invade the Mortal Realm, the strongest demons of the higher hierarchy did not.
So at the moment, after going through the Demonic Encyclopedia that had been engraved into Mercenaries and Adventures from the demons that nearly whipped the people of the earth, during the Dark Age, Rodrick was able to identify the…..creature he was staring at.