Minecraft Dungeons:Soul Sand Valley

The Soul Sand Valley is a secret mission $$, in the Flames of the Nether DLC. It is unlocked through a secret that can generate in the Crimson Forest, which in turn can be unlocked from a secret in the Warped Forest.

Trivia

 * It is currently the only mission that is unlocked inside another secret mission.
 * It is the only Flames of the Nether mission that contains regular skeletons and wraiths.
 * Unlike that in the base game, the speed of heroes doesn't seem to reduce when walking on soul soil or soul sand and they don't seem to change the orange flames made by blazes into blue soul fires.
 * This is one of the only three secret mission in the entire game that have a narration at the start of the mission. The other two are the Crimson Forest and the Nether Fortress.