As a part of the April/May campaign, I was working on dragons. Dragons are one of the few creatures that exist in the MM I ported over.
However, the changes are more than cosmetic:
Dragons society consists of houses and clans. A single god-king rules over all of them. Houses are determined by bloodline to the ancestor from which the House takes its name.
Clans represent individual families within a house. Names are often descriptive (brave, strong, fierce, pure, loyal, wise, etc.)
Dragons are Neutral or partly Neutral in alignment. They tend to be more concerned with their own affairs than the affairs of groundling or sea-dwelling peoples. Any given house has members that represent all five possible alignments.
An individual dragon cast out of their clan for any reason is Otarakan and shunned by all dragons. Otarakan withdraw to isolated places or demi-planes to pursue their own ends. Without bounds, it is possible Otarakan contact each other, but no one knows.
Their intricate organization implies a large number of dragons exist, but sages believe that there are 50 to 100 dragons in existence. Dragons' long lives allow them time to explore all areas of minutae.