JLXC said:
With those simple combat only abilities how the heck could they rule demons?
No.
The stat block lists all of the things the Pit Fiend is going to do in the context of a fight.
The rest of it is undefined as opposed to non-existent.
See, Alatherion the Pit Fiend (in my 4e campaign) has the ability to know exactly where all his allies are and command them telepathically. Without getting confused.
Melkizor the Red, on the other hand, has bound the souls of a Draden cluster and can use 999 of it's Draconic children at his whim.
The Black Mask, on the other hand, has complete control over the city of Night and with effort can alter it's structure.
None of that is in the stat block because none of it comes up in a fight.
All those abilities I mentioned are Rituals, assuming rituals are like incantations.
The 4e stat block isn't telling you how Pit Fiends rule Hell. Just what it can do right here, right now, in this fight.