Formerly Lost Time Series
Book descriptions past book one will contain spoilers, so be warned.

1: Memories of a Lost Time
Streak was only sixteen when Discord betrayed his fellow immortals and tried to take over the world. He joined the army, where he quickly rose in the ranks, eventually becoming the general of the United Equestrian Armies. He had led his troops to victory, becoming the most respected pony in Equestria. That all changed when he was betrayed by his closest allies. He was wiped from the history books and the war he spent five years fighting was erased from memory.

One thousand years later, he pulls himself out of a realm of nothingness called the Void to find the world he worked so hard to help create has fallen completely under the control of one of his former allies. Now on top of being forced to deal with distrust to and from new allies, worry about betrayal again, and being faced with the fact that even he's not immune to love, he also has to deal with an embarrassing new phobia. Whatever it takes to kill the one who betrayed him.

But how will Streak prevail, and even if he does, will he fall deeper and deeper into his darkness, becoming the very monster he seeks to destroy? Only time will tell, but one thing is certain.

Streak will have his revenge.

2: Flight From Memories
Formerly Vengeance From a Lost Time
Celestia had been exposed and stripped of her power. Due to a clever use of Cadance’s spellcraft, every pony, griffon, and minotaur in every city in Equestria knew Celestia for the monster she was. Streak had won. He even managed to survive winning, despite his fears otherwise.

Or so he thought. He left Celestia’s ultimate fate up to the Bearers, which proved to be a fatal mistake. Celestia was spared, given a second chance as a magic-less version of herself, and within days sent an assassin after him, who was successful at slaying the former general. With his consciousness back in the Void, this time as an insider instead of an intruder, Streak learned how to harness his new demon form.

Unknown to him, his death caused a rift in the Bearers. His body was never found, since technically it was not really there in the first place, which led Rainbow Dash to convince herself that he was only missing. She grew resentful as the other bearers, one by one, stopped looking for Streak. When Twilight gave up the search, it was the final straw. Rainbow started an argument that wiped any trace of their friendship from all their thoughts and actions, going so far as to threaten Twilight were she to ever talk to her again.

After two years of animosity, Rarity had had enough. She brought the two of them together to try and rekindle their friendship. This proved to be a horrible decision, ending with Rainbow Dash in jail awaiting trial for attempted murder and Twilight in the hospital. All the while, Celestia was continuing her vile deeds behind everyone’s back. Coupled with the neighboring Griffon Empire closing their borders, to ponies only, without so much as a word as to why, lends itself to a tumultuous landscape for Streak’s return. A return facilitated by one of the the most unlikely sources.

3: Recurring Memories
Starswirl has returned to Equestria, somehow. On top of this, Changelings have moved in and are attempting to do. . . something. Nopony is sure what. To make Streak's life even harder, his daughter doesn't want him to go running through the countryside looking for either party, instead choosing to remain in Ponyville and attempt a normal life.

How will Streak cope with being a civilian now? No more fighting, no more killing, just sitting in town and having a job somewhere normal. Can he even get a job after losing his cutie mark when he transformed into a demon, or is he doomed to joblessness?

On top of this, Twilight is sure to not be happy with the duo, Rarity will have some kind of issues after being held prisoner by changelings, and Star is starting to feel funny around Sweetie Belle. As if his life wasn't hard enough, he starts feeling an urge he hasn't felt in a thousand years. He wants to hurt something, bad.

All in a day's work for Equestria's only remaining professional soldier, right?

4: In His Memory
Streak is dead. He died with a part of the city of Manehattan, but his sacrifice saved the rest of the doomed city.

He left behind Star, however, and she isn't happy that he's gone. Doubly so since Starswirl is the one responsible. Armed with a secret and versatile form of magic used only by the royal guard's War Mages, she sets off to indiscriminately slaughter those responsible for the Manehattan Incident, starting with Starswirl. But has she bit off more than she can chew? How can anyone hope to defeat the former Bearer of Magic in his own element?