Mortis, also Mortis Morgul and Minas Mortis, was a mystical planet imbued with the Force that existed in a kind of dream dimension, or Fantasy Realm, if you will. It was inhabited by immortal weirdos called The Father, The Son, and The Daughter. Due to inbreeding, The Daughter was in fact also The Mother, and The Son was His Own Grandpa. (Darth Saruman possibly lived there as well.)
Mortis has seasons that changed with the time of day. Morning was spring, midday was summer, dusk and evening were autumn, and late night was winter. This played hell with farming, but at least it meant there was a three-minute Christmas every day. Everything was magical and imbued with the Force on Mortis. There were great big Force towers, an invincible Force dagger, Force caves where the dead could speak, and all rooms were equipped with hot and cold running Force, including Force showers and a Force bidet. Force lightning powered a Force power plant that helped power Force toasters and Force dishwashers.
Anakin Skywalker, Obi-Wan Kenobi, and Ahsoka Tano (a.k.a. The Crybaby, The Crazy Old Man, and The Jailbait) visited Mortis once. The Father, The Son, and The Daughter all agreed that Anakin was The Chosen One, whatever that means, and all three of the mysterious entities wanted to have sex with him. They all escaped Mortis somehow, but no one besides the three of them ever saw any planet. It was all a dream! Maybe. Well, we can hope.