Complex sentence: At one point in development, some of the Champions were going to be mythic and much more powerful while others were going to be rare, but it was eventually decided that all the Champions had to be equal in terms of rarity and power.
Split into simpler sentences: At one point in development some of the Champions were going to be mythic and much more powerful while others were going to be rare. It was eventually decided that all the Champions had to be equal in terms of rarity and power.