accidental intrusion. a unique proposal. a boss or those who will come and sometimes the attack. A. offers a reasonable body. attacking other planets and perhaps those who captures the complexity of 100. Attacks rarely.usually those planets that are suitable for habitation. 2 alien invasion. possible to add as alien invaders who attack civilians of the city or the base. may meet at 100 and 80 of a rarity. Three. Offers space pirates. those who like to attack the city or base for the robbery. sometimes attack karabli or stations to profittreasures. 100 complexity can build your city limits.