The only expansion for Twilight Imperium (2nd Edition) introduces two new races -- the Yssaril Tribes and the Mentak Coalition -- and adds shock troops and race leaders, new Political and Action Cards, Deed Cards for tracking income and influence, and new map board tiles including a nebula and a "gravity rift."Shock troops are elite ground forces, and some specifics are tied into Hope"s End, a new planet in the map tiles. Each race has three "race leaders" which are of 5 different types; each adds different abilities to troops, planets, or systems. The "gravity rift" map tile will send ships that enter it in a random direction when they exit.