Is it ever addressed why goblinoids have not developed a dragonmark after thousands of years living on Khorvaire?Dragonmarks aren’t tied to evolution. “Humans” and “Elves” didn’t develop dragonmarks; a handful of specific bloodlines within those races were marked. It’s a mystery of the Prophecy why those specific bloodlines (and races) were chosen.

— Keith Baker (@HellcowKeith) February 8, 2018

Beyond that, there are 13 marks, 13 planes, and 13 moons. Common belief is that these are all connected- which is a reason we haven’t thrown in additional marks. In my Eberron, for a new dragonmark to appear, one of the existing ones would have to disappear.

— Keith Baker (@HellcowKeith) February 8, 2018