Quote:
GuildMag: Primordus was the first one to awake. While (most of) the other dragons moved places (be it raising a continent or flying south), Primordus decided to stay in the Depths of Tyria. Why did it decide to stay there?
Jeff Grubb: Primordus has remained beneath the surface, but that doesn’t mean he hasn’t moved around. He has been clearing huge tracks of the underground regions of the world, and his activities have sent a number of other races to the surface, including one that the asura are all-too-familiar with – the rodential skritt. As a result of his activities, the minions of Primordus can be found almost anywhere on the surface.
Jeff Grubb: Primordus has remained beneath the surface, but that doesn’t mean he hasn’t moved around. He has been clearing huge tracks of the underground regions of the world, and his activities have sent a number of other races to the surface, including one that the asura are all-too-familiar with – the rodential skritt. As a result of his activities, the minions of Primordus can be found almost anywhere on the surface.
http://www.guildmag.com/gmblitz-lore-interview-with-jeff-grubb