Combine Cell

Combine Cells are used to hold prisoners or humanoid troops/servitors where they are normally found in the Citadel and in Nova Prospekt.It is first seen in when G-man was placing Gordon in City 17.

Half-Life 2
When the capture of a resistance members or disobedient civilians are placed in cells they will be either be processed to Stalkers or Overwatch troops or awaiting to be killed. The inside contains a straight jacket device that holds the prisoner. When Gordon made it to the newer compound of Nova Prospekt with Alyx they found many civilians in the cells sleeping until they found Eli also in this state, it would seem that induce a drug in the cell to make prisoners sleep for unknown reasons.

Trivia
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 * The structure of the cell appears to be based off the Iron Maiden a torture device in the medieval era
 * In the concept image (below) shows the cell oozing blood hinting that it was originally the cell was to be an Combine way execution.