If you are looking for a fresh questline in Starfield where you uncover the mysteries behind a mutated species of a creature, United Colonies is the faction you need to join. Unlike most other factions, United Colonies sends you to a fight against a set of deadly creatures called Terrormorph that could soon turn into a threat against humanity across all star systems.
Starfield: United Colonies Vanguard Quest List
Can you stop Terramorphs?