Before the rule of Discord, before the Alicorn sisters were even adults. Transported to the world of Equestria long ago... a lost human adopted into the Royal Family loses his sanity and makes ponies pay with their blood for being the racist flanks they are until his banishment. His magic fueled by his need for justice and anger, now dwindled down to embers, is now back and has missed his step-sister's entire lives. Time to catch up with them and relearn his powers to benefit the Kingdom and earn his role back as Prince Shadow Flare and his new kingdom... The Everfree Forest.
PS Derpy will show up later and will be the main interest... may or may not become herd story.