The effect of the "Zodiac Souls" activate when they are more "Zodiac Souls" in the Graveyard. They are based on the Star Zodiac signs.
We had the Archfiends, but compared to the Chess monsters, they are much less strategic. The Chess monsters may seem weak, but they are very strong if you are the strategic kind.
Introduction of "Story" cards.
Basically normal effect monsters, but Story monsters have a story line, and that makes them much more important...