TModLoader

tModLoader is a free modding tool that is developed by the TML team and released by them as a standalone program, and can also be obtained on Steam as Terraria DLC. It can be used to download mods from their database, called the "Mod Browser", receive updates to mods if there are any, or upload your own mods to the Mod Browser. The official wiki, with information about creating mods and using tModLoader, can be found here.

Items
tModLoader adds some assorted items, though none of them particularly impact the game.


 * The Unloaded Item, which is used to store data for modded items that no longer have their mod present.
 * The April Fools Joke, which appears to be a Terrarian but actually can be used to inflict the Wet, Lovestruck, Stinky and Slime debuffs upon the player.
 * The Starting Bag, which is used to store excess starter items that would not fit in the player's inventory.
 * Various tModLoader Developer items.