“Sombra was traveling with Radiant Hope to find the missing shards of Princess Amore’s statue in the hopes that they would revive her and reunite her with her niece, Princess Cadence (yes, Amore is Cadence’s aunt in my Age of Equestria continuity) and that she would forgive Sombra for what he did 1000 years ago. However, during their quest in a blizzard at the North, they came across Emperor Grogar who threatened Radiant Hope and forced Sombra to put on The Alicorn Amulet to become a demonic shadow Alicorn who’d be referred to as either The Shadow King, King Sombra, Lord Sombra, Emperor Sombra, or The Umbrum King. Emperor Grogar needed Sombra’s help to release the Umbrum to have them conquer the Crystal Empire and spread fear, hatred, and darkness across the North. Grogar had been told by Queen Chrysalis that Sombra had been reformed after IDW’s MLP: Siege of the Crystal Empire, and the demonic ram used his dark magic to get The Alicorn Amulet from Zecora so he can use it to corrupt Sombra and turn him back to evil to make him cooperate with Grogar and his Dark Alliance and help them on their quest to destroy ponykind, annihilate Equestria and turn it into a utopia renamed New Tambelon where creatures and monsters can roam free and have all the magic to themselves with Emperor Grogar as their ruler once the ponies are doomed to extinction and the Elements of Harmony are gone forever.” - MelSpyRose/PaintStroke203

King Sombra, My Little Pony: Friendship is Magic © Hasbro
Alicorn Amulet King Sombra, My Little Pony: Age of Equestria series © MelSpyRose