The Queen is a red and black spider-like creature included in the SDK. It is fully animated, but does not make an appearance in the initial release campaign, Jacob's Rest. It has five health bars and can lock players into place while dealing damage to them with tentacles that come out of the ground. It can also enter a "crouched" position to fire a volley of 3 acid shots. It is a boss-type enemy that would have appeared in the unused SynTek Labs map.
- A marine can escape from her tentacles by using their melee attack.
- A sound file (sound/vo/command/co_debriefing_ob10.wav) related to SynTek Labs mentions "We are still detecting a single large heat source in a deep well protected chamber...". This suggests the Queen's existence has been planned for the final Alien Swarm release, but was cut along with the SynTek Labs level. This may also explain the lack of a 'polished' model, but a fully working AI.
- Some parts of her body are similar to the Alien Queen from the movie Aliens.
- The Queen was intentionally supposed to be known as the "Behemoth", with a large sac (as labelled in the alpha concept) giving off a more obvious Alien Queen look.