Inside of the fortress, Ed and Al are taken to the infirmary, and Ed is warned about the effects of the extreme cold with regard to his normal automail. This is in contrast to Buccaneer's automail which was made to endure these conditions. The brothers then meet with Major General Olivia Armstrong and tell her the story behind why they're there, though they decide to leave out the parts about King Bradley and the Homunculus. Olivia doesn't really want them around, but she is interested in the applications of Eastern Alchemy, so she agrees to help them find May Chang. In the meantime, she puts them to work and leaves them with a subordinate named Miles who, when Ed pries, reveals that he's got some Ishbal blood in him. Despite this, Olivia had kept him around because she felt that this was not the kind of place for discrimination. Miles now assigns the brothers to remove dangerous icicles hanging from the ceiling, and while attempting to do so, the brothers run into Falman who's got the same job. Afterward, he shows them around, taking them to the technology development area where several tanks are being worked on and also to the fortress's lowest level. While down there, the three of them witness something emerge from the ground: the Homunculus Sloth.
Ed and Al think at first that the Homunculus is after them, but they soon realize that Sloth doesn't even know who they are. Sloth instead has been digging underground and now isn't sure of what to do in this unfamiliar place. With bullets not slowing him down at all, Sloth heads up an elevator to the technology development area, and everyone follows him there. News of the intruder reaches Olivia right as she is getting word that Kimblee is in the area and wants her cooperation. She first tries to stop Sloth with a rocket, and when that fails, she jumps into and commands a tank. Even tanks shells have very little effect though, and Sloth counters by punching debris in their general direction. Ed uses alchemy to protect some of the soldiers from being crushed, and he then tries to tell Olivia that Sloth can't be killed. She in turn questions what Ed knows about all this, but he refuses to tell her anything specific about the Homunculus. What he does say is that he doesn't want to see the people there get killed, and he guesses that Sloth has the same body structure and composition as a human. This is all Olivia needs to know to prepare a plan involving tank fuel to stop her opponent.