Planetary flora and funa that you have to eather fight or research technologies in order to remove if no a big penelty will be inplace. EX Desert planet could have large wrom/snake beasts if not taken care of they give off -5 to all types of income (Food, sci, pro ect) you will eaither have to ground battle them or research a tech for getting rid of them. This could make planet that seem perfect have a down side to, now the players will have to consider looking for less perfect planet or fixing the one they found. You can even base a major or minor faction around the beast and have them capture them and use them as weapons like the riftborn do will there time zones. Maybe even toss in some system beasts? would love to get into a new system and just see a gaint space fish! <3