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The Ghosts, not to be confused with Ghost from TimeSplitters 2's NeoTokyo, are non-playable enemies encountered in What Lies Below.

Their only attack is floating towards you until they touch you. The attack is a one-time deal as they perish afterwords. However, the danger from them is the fact they completely invisible and are immune to practically everything.

The only to harm and see them is the use of a Ghost Gun