Russel.

While helping Eli Vance steal a Combine reactor, Russell stumbles upon some images of a mysterious building. This discovery causes a Combine raid that Russell narrowly escapes, but Eli and Alyx Vance are captured. Russell frees Alyx, gives her a communication device with the help of his drone, and escorts her to his lab, where he devises a plan to rescue Eli by sending Alyx through the Quarantine Zone. He then gives her the Gravity Gloves, or "Russells," to assist her on the journey, as well as a gun for her to borrow. For the rest of the game Russell communicates with Alyx over the radio, sometimes commenting on her surroundings or offering helpful information to help her on her journey.