On an Earth-like planet, there were humanoids. They themselves evolved from reptiles. Now, this is happening in reverse. That is humanoids are turning into reptiles. But not your ordinary reptile. The humanoids are turning into dragons of all different kinds.
Ice dragons have the ability to freeze anything with their breath. Because of this, they can cryopreserve dying dragons until a medical dragon comes by to heal the dragons. This can be from a few minutes to years. Ice dragon eggs can only hatch in really cold places.
All dragons come from eggs although certain things trigger hatching and others delay or stop it. Once the egg has hatched the dragon is tiny compared to its mother and gets nutrients from stuff close by. For Ice dragons, it is food that is frozen by their mom. The dragon gets longer and taller. The back legs grow faster than the front legs and a few years later those front legs become arms. 2 more limbs then start developing halfway between the legs and arms. These limbs eventually develop into wings. From this point, it is just size and mass respectively that changes until it is an adult. Mating habits differ from species to species. Ice dragons make a big nest and freeze it. The number of eggs in a clutch also differs from species to species. Ice dragons only have 1 egg in a clutch.
How would Ice dragons freeze anything with their breath other than themselves?