Mysterious Room
Explanation:
1) When you first construct the Mysterious Room it begins at Renovation level 0.
2) Mysterious Rooms begin with 2 Slots for Artifacts to be Housed.
3) For each renovation level, you gain an additional 2 slots.
4) You may not gain or acquire artifacts until you have built a mysterious room in at least one lair.
5) An artifact that you own, but do not want to use in your Mysterious Room can be stored (1 Slot) in your storeroom. See point 4.
6) For further information on how Artifacts interact with the Mysterious Room, see: Artifacts
7) Having a Mysterious Room alone grants points towards the 'Artifact' Victory Point count. Though, very few.