A regular addition in our plays. I'll break down the four components that this expansion adds:
The Dragon: An interesting take-that mechanic being added into the game. Suddenly, it's possible for your meeples to be removed from the board through bad planning/luck. Quite enjoyable, leads to a lot of fun "DAMN YOU" type moments. The big dragon meeple is excellent
The Fairy: a little white meeple that you can place onto any incomplete feature when you lay a tile without placing a meeple. You get one point at the beginning of your turn if the fairy is still on one of your features, and that feature is protected from the Dragon. That gets a bit fiddly and easy to forget, but it's not a huge issue. The biggest problem I have is that it's so easy to get a Dragon tile and place it without laying a meeple, and then you get to take the fairy away from an opponent before starting the dragon rampage. It's a bit frustrating, because it makes it hard to really plan against the dragon attack.
Princess tiles: When you place a princess tile into an incomplete city, you can remove any one meeple from that city. This can leave a city unoccupied, or help you obtain a majority. Pretty handy.
Portal tiles: They allow you to place a meeple into any unoccupied incomplete feature. Very cool.