How do I spawn the Truffle?

Solution 1:

As per the wiki, Truffle requires a vacant house built in an above-ground surface mushroom biome before he will move in. The world also has to be in hardmode (i.e., the Wall of Flesh must be defeated).

A mushroom biome can be artifically created by collecting a bunch of mud and placing it wherever you want the biome to be. Then take some blue mushroom seeds (found in natural mushroom caves underground) and plant them in the mud you just placed. It might take some time, but after a while the mushroom grass will spread to the rest of the mud and the biome will be complete. You can tell when the biome is finished when the screen darkens near the area and the music changes.