That's probably the ritem.dat file.
It lives in the M2Server directory the same as the mir2.exe and also an exact copy must live in the data directory of the client.
If you don't have this file, you make it by right clicking inside a running M2Server.exe and selecting the Create New Data File option.
The file is created and placed in M2server directory where it should be. Copy it to your client as explained above.
Whenever you make item changes such as stats, item images etc., create a new ritem.dat and repeat as above.
If you make item changes and don't recreate the file, you'll start to get errors of ghost stats, images, and shops will have display errors too. These will be rectified by the new file. However, if you rename an item, you can't always delete it or drop it afterwards as your item would no longer exist. Use the clear bag command or physically remove the item from the SQL database if it persists.
After making wholesale changes to items, it's good practice to delete the saved NPC files such as the contents of Market_Prices and Market_Saved, then restart the server. (Not the Market_Def !)
