As a lot of you guys know I ship Echotail (Echofrost and Brackentail), and one of the things standing in the way of that happening is the fact that, wile Echofrost is leading Storm Herd across the dark water, Brackentail stayed in Anok. This got me thinking of ways Brackentail could possibly have a reason to make the long and dangerous journey to go after Storm Herd, here are some of the theories I've come up with:
When Morningleaf gives birth to Star's foal, a colt. It takes the couple only a few minuets to realize that the foal is identical to Bumblewind, in not only looks, but personality as well. So Star sends Brackentail with a few other steeds to tell Echofrost about Bumblewind's double. After the steeds deliver the news to Echofrost, Brackentail decides to stay with Storm Herd
Star decides that there needs to be communication between River Herd and Storm Herd, so he picks some of the fastest strongest steeds to use as messengers, and Brackentail is one of them. On one of his first journeys as a messenger, Brackentail decides that he is needed in Storm Herd so he stays.
A black foal, a mare this time, that was long since believed to be dead, returns to Anok after being in hiding for two hundred years. Star welcomes his fellow black foal in to River Herd, but after years of being tormented the mare refuses and starts killing steeds with her silver starfire. Almost all the River Herd steeds died, and the survivors, witch are Brackentail, Star, and Morningleaf, flee across the dark water.
Storm Herd looses most of it's steeds in battle, so Echofrost sends a messenger to ask Star for help. Star sends a few hundred steeds, led by Brackentail, to help Storm Herd, then Brackentail decides to stay.
Brackentail gets tired of being avoided by his herd mates, so he leaves River Herd to find River Herd in hopes that he will be more accepted by Echofrost's herd.
These are just the theories that made the (more or less) most sense, but who knows, Brackentail might return for something no (except Mrs. Alvarez) has thought of yet.