In some RPG games, treasure chests have random contents. This is more a realism thing as you wouldn't find "THAT" sword able to kill a dragon in a treasure chest in real life. it would be probably full of junk. Making random treasure is surprisingly easy, and you only have to make it once. As you can copy and paste your random Treasure chests wherever you desire.

Fortunately, Enterbrain slipped in a quick treasure chest generator. This can be the base for our random chest. See the event command:
Change items:+__[____] Or something along those lines? This is were we need to edit this for Randomness. How? go into the database and create a new Variable or common event if you have already made your random chest. You can call it whatever you like. "Treasure Gen" or "Random Treasure" would be a sensible idea, Or something along those lines.So you don't delete this variable.

Now, Remember, what ever you want to NOT Get out of a treasure chest, put on a really high number so it is not inconvenient so you have to make multiple random generators, But not specify any of the number ID'S of the items. Such items would be quest items. Unless it is a random collection quest now when the player opens the chest, randomly set the variable, then reward the item in that number slot.

want the Player to get nothing but junk out of some chests? Create a item that does nothing or something very useless and Name it "Junk" or "Rubbish" Whatever. This can be added into the items and got out of the chest at random.