A recurring nightmare convinces Luna that, since her return, she has never regained her sister's complete trust. And at the forthcoming Festival of the Eclipse, she decides to make amends with a bold gesture.

But Luna's solution causes consequences she never anticipated. Consequences the whole world will feel. Now, Celestia and Luna must set forth on an adventure that will take them even into Tartarus itself, and set everything right before it's too late.

And if they're lucky, they'll rediscover the trust they once had a thousand years ago.

This story is a sequel to Project: Sunflower

After the events of Project: Sunflower, Erin Olsen has returned to Ponyville, happy to pursue her studies in magic. After everything that happened the year before, she's looking forward to spending her days studying and having fun with her friends.

Meanwhile, on the newly discovered world of Harmony, humans and ponies work together to study this strange new world. However, their arrival causes something ancient to begin stirring. Something that may end up changing everything.

Erin will need all of her courage, all of her cleverness and, of course, all of her friends to see herself through what happens next.

Cover art by Valkyrie-Girl
Editing provided by:
Brilliant Point, Coandco, Ekevoo, Ludicrous Lycan, Merlos the Mad and Razalon the Lizardman.

It is the year 2038, and the Earth is slowly being consumed by a space-borne monstrosity dubbed the Black Tide, which is using nanotechnology to remake the planet into something hideously alien.

Erin Olsen works for Project Harmonics, humanity's last-ditch effort to find a new world before the Tide can wipe them out. But when that world is found, and it turns out to be occupied, Erin will need to find the courage to face the unknown in order to save the inhabitants of both worlds.

(Many thanks to Easteu for the fantastic cover image for this story!)

Now with its own TV Tropes page

There is now a follow-up to this story: Sunflower - Side Projects
Sequel: Project Sunflower: Harmony

4131 EC, a year of no importance. Thousands of years ago, the entirety of our universe consisted of a single planet, an idyllic world of harmony and peace. Now, the galaxy is a hard place. The Age of Harmony is over, the old order is dead, and all that’s left of our once glorious civilization are fractured states in decline.

My name is Horizon Seldat. I grew up on a slum colony orbiting Luna six. My life just got a little complicated.