You start as a Federation ship carrying information which is vital to the survival of the Federation, and must progress to the eighth sector to deliver it to the commander of the Federation fleet. The Federation is composed of a group of races united in the galaxy to pose a great strength in numbers and are the main protagonists in FTL. They have no oxygen room, so boarding them is dangerous. The rebels also use AI ships, which are dark gray robotic ships built by the rebels to scout ahead of the fleet.
Rebel ships can be identified by their orange hull and cyan stripes. The most powerful enemy in FTL is the Rebel Flagship, which is also the final boss. If you are caught by the rebel fleet, you will have to fight an elite fighter, which is a more powerful version of the rebel fighter. As you progress through the sectors in FTL, you will be pursued by a rebel fleet which will follow you as you play. They are rebelling against the Federation for currently unknown reasons, and have almost destroyed it.
The rebels are the primary antagonists of FTL.