Doom Train is the 3rd level in W5 of SMFR, Midgard. It's a train of doom. I'm so good at explaining things.
The level starts with a Message Box telling what the train is. Mario/Peach boards the train (for some reason) and the player is taken to a puzzle room. After the puzzle, there is a soul you can talk to. Most of the rest of the level consists of Spiky ? Blocks and bridges. There is an area taking place inside more train cars, and from there it is mostly jumping, and avoiding Boos and Souls. The end flag is on a bridge, which takes Mario/Peach to the locomotive, ending the level.