The first expansion for Twilight Imperium (Third Edition) features four new races that are unseen in previous editions, more balanced Strategy cards, more belligerent Objective cards, several new surprises for neutral planets, two more sets of plastic units, rules (with more than a dozen new optional variants), and enough additional systems for a fourth ring around Mecatol Rex. Now it's 3-8 players. If you played TI3 and had some ideas for potential improvements, they are probably incorporated in Shattered Empire.