Alyx Vance, and later through her marriage with Gordon Freeman, Alyx Freeman, is one of the members of the Earth Freedom Fighters. She is portrayed as a woman in her mid-twenties, and is a prominent figure in the Resistance campaign against the rule of the Axis (namely the Combines) on Golmar Earth. Alyx is a skilled hacker: she is able to operate and manipulate technologies such as turrets with the help of her gear, and also wields an EMP Tool used to perform a variety of tasks. She is also very proficient with a pistol, and hand-to-hand combat, as she single-handedly defeats six Combine Civil Protection officers. she is also fairly skilled with the use of Sniper Rifles, where she provides cover for the Resistance soldiers.
Her disappearance following her deal with the G-Man to save her father was something that resulted in her lack of involvement for much of the war, and becoming a center of a massive search conducted by her father and Gordon, but near the end of the war, both managed to find her and free her but becoming aware of the larger implications and roles they share in the Multiverse history via Old Gray, the employer of the G-Man.