Its also worth noting that some NPCs have explicitly been given game breaking Illegal abilities. I know back in 1st when they published the adventure with Harlequin in it the book said he did not have stats and the PCs lose period full stop if they engage him. It said he can TELEPORT and yes they meant the TELEPORT that was explicitly forbidden in the spell creation rules because he was using 4th world magic and he knows how to do things that were forgotten at the end of the 4th age and only other people like the Great Dragons who survived the jump from the 4th age to the 6th age know the stuff he knows. The PCs could have multiple nukes and Thor shots on call and they lost to Harlequin and he slapped them around until they did what he wanted or he killed them out of frustration/boredom.
Heck when the gave him a stated write up in street legends in 4E he was a Grade 30 something initiate and had a force 24 ish ally spirit with him. And implied pretty heavily that he had meta magics that were unknown to the current age and filled any gaps the GM needed plugged.
Bit of a sidetrack here, but is anyone else explicitly okay with certain famous/powerful NPCs having abilities or fluff that breaks the standard rules? I mean, in most history of tabletop it exists somewhere in the books something that says "The first rule is to have fun. As long as the players and GM enjoy the game, feel free to fudge the rules a bit."
I mean Hell, you look at any published adventure, especially the older ones, and there are significant parts where "X happens" no matter what the players do. So having an NPC or event break the normal rules I think is fine, as long as it's stressed that it's extremely rare/expensive/challenging to do that, and /orthe Powers That Be have tried recreating it with little success. Biggest thing is for them not to abuse the rules or start using the tabletop Deus Ex Machina so much that the normal rules become irrelevant.
The issue with Harlequin, IMO, is that they used what should have been a singular instance of that same NPC/rules Machina and made a character that was the focus of 2 entire adventures. So if/when the party eventually tries to challenge him or go against his wishes, the writers simply said "He wins, they lose, thanks for playing".
Bear in mind that this was still in the era of Gygaxian "player vs the GM" mindset a bit, so making arbitrary rulings like that was more common. I mean shot, look at the original Tomb of Horrors as a prime example of the Treadmill of Fun.
Anyway, I'll get off my soapbox now so we can get back to the topic at hand.