The Invisible Sentinel Beam is a weapons used by Enforcers in Halo 2. The beam, which is only used if the Enforcer's Heavy Needler and missile launcher have been disabled, is invisible, but it inflicts the same amount of damage as a Sentinel Major's beam. Blue sparks are emitted from where the weapon should be. The beam cannot be used by players after the Enforcer is destroyed. It is clearly a last resort, used by an Enforcer only when it has no other means of killing the player.