(Psi)SeveredHead
Adventurer
I wouldn't be surprised if the highest CR thing is a gold dragon... unless they don't appear in the MM (it's not like I'd miss them).
Dragons are top-of-the-scale in terms of complexity... but so are fiends.
I think dragons are just hard to write plots for. Dragons used to be loners who spent most of their time living with their gold and, while sometimes intelligent, didn't do anything more complicated than extort villagers and kidnap their virgins. (Only top of the line dragons did anything more complicated, from what I've read.) Unfortunately in DnD, dragons are used to fill the same role as fiends; manipulative shape-changing masterminds with rafts of minions (often leaving behind half-dragon offspring with the weirdest creatures) who have a lair full of unique magic items along with the gold. Why make them into new fiends when fiends already exist and are cooler when they pull off the "Magnificent Bastardy"?
Dragons are top-of-the-scale in terms of complexity... but so are fiends.
I think dragons are just hard to write plots for. Dragons used to be loners who spent most of their time living with their gold and, while sometimes intelligent, didn't do anything more complicated than extort villagers and kidnap their virgins. (Only top of the line dragons did anything more complicated, from what I've read.) Unfortunately in DnD, dragons are used to fill the same role as fiends; manipulative shape-changing masterminds with rafts of minions (often leaving behind half-dragon offspring with the weirdest creatures) who have a lair full of unique magic items along with the gold. Why make them into new fiends when fiends already exist and are cooler when they pull off the "Magnificent Bastardy"?