Item Duping

There have been few confirmed ways to duplicate items on Tibia, despite how often players claim they had done it.

Black Knight Door Trick
There was a claimed way to duplicate items using the Black Knight door trick. (Please edit and add information on this trick if you have it available, I have searched around and only found mentions of this trick, with no formal explanation.)

House Duping
There was another way that item duplicating was discovered on the server Nova, by Messiah, during one of the first great Nova wars. Messiah discovered this trick in his house, during a server save. (Presumably on accident) The trick worked like this. You would wait until just moments before server save. On Nova, server save at the time was 3:00:00 AM EST (GMT +5). So you would wait until approximately 2:59:30 AM EST, and throw an item on the ground of your house from your character inventory.

When the dupe was successful, you'd have the item in your inventory and on the ground of your house after the server turned back on after save.

This is most likely because character inventories were saved just before the server save "kick-off" would occur, then house decorations would be saved shortly thereafter. Supporting evidence to this is that after the "fix" was applied, characters would stay logged in during the server save, even though the players themselves were kicked off. It's assumed that the character inventories would not be saved until the player was no longer actively in the game, to prevent these types of duplications from occuring.

It was through this method that Messiah was able to have so many Amulets of Life and backpacks of mana potions at the time. This enabled Messiah to have the highest magic level in Tibia at the time. (76) It also contributed to earning him the nicknames "The Mana Cask" "The Human Mana Cask" etc... His war strategy was often to drop into large enemy groups and use Ultimate Explosion (exevo gran mas vis) over and over until they all died.