Looking for story

I remember this one story about Twilight finding a male alicorn in Tartarus and freeing him after learning he's the first inmate and that Tartarus was built for him. After being freed he's shown around the changed world eons after his time and he decides to get his friends to this era as well. His firneds include a Phoenix, a giant dragon/lizard who's waking wrecks the dragon alnds and a Leviathan that was sleeping at an abyss near Mount Aris. Tirek, Cozy and Chryslais are also in it and they get redeemed but I can't remember the specifics.

There's also a sequel in which the Alicorn an the phoenix travel to other countries to see what else has changed, including a visit to Gryffonstone where they retrieve the idol and Saddle arabia.

For the life of me I can't remeber any of the names of the story or the characters. Anyone have any idea?