Dragonborn

While dragon's are rare in Theros, they do exist. Blue dragons made their dens near coastlines, preying on anything that enters its territory. most experienced sailors have found ways over the ocean circumventing the dens of these fearful creatures. Some red dragons exist on the top of some volcanic mountains. some cults revere the creatures and try to make a strenues alliance with the creatures through gifts and sacrefices.
Some tell stories of the bleached prophetic dragon, but not much is known about it.
Most of the small number of existing dragonborn are either Red or Blue, some tell tall tales of encountering gold and silver dragonborn however.