I think that The Warlord or Merchant Curisities should bring so type of Star that Decreases the exp that a player receives by a lot (may be diferent stars for diferent amount) and it'll be understandable if the max number of star you can buy is 5 (or something similar) every time they come.
This star would make the game much more fun and less stressing over leveling up.
And it'll be much more better if this Star has a lot of time and that a player can make a profit out of it.