This story is a sequel to Lost into Shadow

The impossible has happened, through all the pain and darkness, Twilight Sparkle succeeded in her impossible mission...mostly. King Sombra is still plenty rough around the edges, but despite being an old dog he's making an effort to learn new tricks. Where will this new way of life take him? He has absolutely no idea, but with his queen to guide him, what could possibly go wrong?

This story is a sequel to Lost into Shadow

Twilight has failed, or rather, she has succeeded. Her darkness is her power, and together with her husband, Queen Twilight has a new plan for all of Equis. The black castle rises to greater power than has ever been seen before. War is brewing while alliances are forged and others are broken. The days of harmony are dead and gone, and all the world will be forced to mobilize against the might of the Nightmare Hordes. Will they prevail in the faces of Wrath and Despair? Do they have any hope of someday returning to a time of peace and love?
....
........
Not a chance, because in Chapter 1, Hope dies.

Twilight had reached her peak, she was at the happiest point in her young life. The day of her coronation as Equestria's newest princess had finally arrived. Then the unthinkable happened, Sombra appears in the throne room alive and well demanding his chance to be reformed by pony society. The unthinkable happens again, when his wish is granted, spearheaded by none other than Princess Twilight herself. Will Sombra's nefarious plans bring her to ruin, or will she succeed against all odds? Only time can tell as it reminds them both that plans have a way of changing all on their own.