Not only was Gaith harder to deal with than Rend, but he was also a Chromatic dragon.
In Dawn, the Dragon race had five main types, as well as a few other subtypes.
Firstly, there was the Nether dragon. In the Second War, Deathwing stole the dragon eggs and went into the Nether. There, they were exposed to arcane magic, mutating into the Nether Dragons. Those that did not mutate were killed off by Gruul the Dragon Slayer.
During this time, Deathwing was defeated by Khadgar and escaped back to Azeroth. Because of the special conditions, Nether dragons were not affected by the Ancient Gods and therefore, they were no longer members of the Dragonflight.
