The mystery set is indeed a mystery. When released each of the 15 levels contain something
special in them.
geoo89, I liked the first level "Captured by Pillars". Nice trick used there!
Unfortunately I couldn't beat the other levels yet; they were quite hard.
Here's
Sets 1 and 2. These levels are quite fun, especially when going for 100% in them. Both sets use a lot of different styles.
Set 1 contains 40 levels. They use a lot of different styles, but none of them are Lemmus styles. As for the levels, a lot of them are quite fun. Some fun ones are "Bublaria," "Get to the Portkey!," "Wacky Walls," and more.
Set 2 contains 24 levels. Some of the levels were not as fun as the ones in set 1, but 99% of them are 100% possible. One level is very special, as it contains two characters from two movies.
UPDATES: "The Retarded Level" is now Level 26, and I've completely rejected the level "Needles," and replaced it with a new one, "Up the Top," which is Level 24. For set 2, Level 15 has the new level, "Any way you want!" with a few rearrangements in the set.