Starfield has perhaps Bethesda’s best main narrative yet, however, most people will still prefer to spend most of their playtime going through the various faction questlines. Among all the different groups out there that your character can join, one of the earliest and most appealing is the UC Vanguard. During one of these faction quests called “A Legacy Forged,” you will have a critical decision to make regarding the use of either Aceles or Microbes to stop the deadly Terromorph threat. The consequences of which one you pick won’t be made clear until after you commit, so here are the repercussions of each decision in Starfield.
The Terromorphs are a created species designed to completely destroy whatever environment they encounter and must not be allowed to propagate. To contain this threat, Abello from the UC Council presents you with two options to destroy the Terromorphs: Aceles and Microbes.
Aceles are another species that is the only one capable of hunting and killing the Terromorphs. By allowing them to breed and hunt down the Terromorphs, you can end the threat safely, but over a longer period and at a higher cost.
The Microbe mentioned is a bioweapon that will infect the Terromorphs essentially all at once to wipe them out. However, the Microbe will also infect any nearby flora and fauna, essentially killing anything else nearby as collateral damage. It will end the threat in one shot, yes, but at the cost of many innocent lives as well.
Both will result in the Terromorphs being stopped, but the choice comes down to whether you want to deal with it in a more “natural” way by using a natural predator or dropping a chemical bomb of sorts that is indiscriminate in what it will infect. Your choice won’t impact your reward or the narrative beyond this, though some Companions may not agree with one choice or the other.