The Clone is an ally and enemy of the Marine in the Campaign. In Level 21, the Marine is cloned. If the player has not bought it yet, they will receive a Defibrillator to revive this ally. He carries the same weapons as the Marine and, initially, shares the same enemies as the Marine. The clone is controlled by the AI but the player can press TAB to control the clone.
Seconds after Level 22 begins, the clone begins to shoot at the Marine without warning. After killing his clone, 2 more clones teleport near the area and 2 other clones teleport in the far right side of the level. They are all armed with the fully upgraded Ray Guns whereas the original clone had all of the Marine's weapons. These enemies are difficult to destroy, as their weapons are very powerful and they have the same amount of health as the player. When the level is finally cleared, the clones are never seen or heard from again in the campaign. It is possible that the clones were wiped out and/or the project was abandoned.
- It has been confirmed by Eric Gurt that the Civil Security made a visual copy of the Marine's suit and put a regular soldier inside of it as an attempt to trick the marine with fake teammates, even though the Marine never had any teammates that had the same appearance.