Four mysterious artifacts.

the artifact isn't four, but (!) five. The fifth one is located at the bottom of the sea (the last quest) under the sunken ship. (there's a chest hidden right below the waterline). It's called "Temple in a Bottle" and it teleports you to a secret location, a kind of joke from the developers. In this temple, there's an exit to Harmonade, and all the NPCs are people (non-interactive clones), as well as chests with infinite jewelry, and two "supermen" – Robert the Wise and that dark one. There's also a trick with infinite gold (two bots facing each other, one sells crates, the other buys them). And there's a room with NPC parodies of all the heroes from movies and commercials of that era. In short, you can have a lot of fun there, it's a pity that this gag is at the end of the game and not at the beginning, like in the sixth part.