The end of the United Colonies quest line in Starfield is centered around you trying to deal with the recent Terramorph problem that has emerged. The ancient beasts are popping up all over the Settled Systems and you need to figure out why and how to stop it. Through some clever detective work, you will eventually who is responsible for the attacks.
However, the quest line can’t end until you decide how to deal with the Terramorphs in Starfield, which forces you to pick between a Microbe or the Aceles.
The Microbe is a pathogen that scientists will release into the air across the Settled Systems. It will effectively kill any remaining Terramorphs along with the Heat Leeches that you’ve learned are the root of the Terramorph problem. Although, there exists a small chance the Microbe could mutate and become another issue entirely. On the other hand, the Aceles are a race of creatures that have wiped out Terramorphs before, but releasing massive animals like them into public areas could prove deadly for some citizens.
Picking between the Microbe and the Aceles in Starfield
You are forced to make this decision all on your own, though Hadrian, Percival, and some UC Cabinet members will chime in with their thoughts. After some debate, the UC Cabinet will turn to you and your decision will basically decide what direction they take.
Fortunately for you, it really doesn’t matter which option you pick here. Whether you go with the Microbe or the Aceles, the outcome of the UC quest line remains the same. If you decide to go with the Microbe, then the pathogen will be released while choosing the Aceles will start the cloning process of the creature.
You won’t see the effects of your decision, so I would simply go with whatever you think is the best choice. I chose the Aceles option, as it’s arguably safer than the Microbe. While the Microbe is more effective, there exists the small chance it could mutate into something else. The Aceles have wiped out Terramorphs before, so I thought it wise to let them do it again.