The Gods Packs
The Gods' Packs existed in the past and were the result of humans and Messengers working together in order to serve the Gods. They ceased to exist after the Breaking.
Sean briefly explains the history involved in Chapter 11. According to Messenger Lore, the Gods created the world and everything within it. Their favoured creations were wolves and humans, both species were given powers and can be classified as Messengers in a broad sense. The Gods found their powers in the world were limited, so they entrusted most of their meddling to the wolves and humans who served them. Humans and wolves combined their efforts as The Gods' Packs.
They managed to co-exist for some time, but it wasn't long before the balance of power began to shift and in-fighting began the Breaking.