The Cycloid Sentry is a miniature version of the Cycloid Emperor, bearing the same relationship to the Cycloid Emperor that the Battlelord Sentry bears to the Battlelord. It wields the same attacks as its boss counterpart.
The Cycloid Sentry first appears on Bloody Hell, the third level of Alien World Order. It makes the fewest appearances of any recurring enemy; across the course of the game, there are only four cycloid sentries, three of which only appear on higher difficulty settings.
In the authorized Duke Xtreme expansion, two cycloid sentries appear on the level Sanitation Plant, and in the expansion Duke!ZONE II, one can be seen on the level Banzai, but these enemies are not identical to the canonical cycloid sentries introduced in Duke Nukem 3D: 20th Anniversary World Tour.
The Cycloid Sentry is a smaller, weaker version of the Cycloid Emperor. Like the Cycloid Emperor, it can rapid-fire rockets from its cybernetic appendages, and it can spray clouds of psychic projectiles from its mouth. It also exhibits the Cycloid Emperor's tendency to fire its weapon in response to damage.
The Cycloid Sentry is more likely to use its psychic blast at close distances or if the player is in the same sector, and it is more likely to fire its rockets if the player is far away.
The Cycloid Sentry is a particularly slow enemy; it is noticeably much slower than the Battlelord Sentry.
Unlike the Battlelord Sentry, the Cycloid Sentry is capable of self-inflicting damage with its explosives. It requires only ~6-7 of the Cycloid Sentry's own rockets for it to kill itself. Because all of the Cycloid Sentries in the game are placed behind barriers, they can be reliably led to kill themselves without costing the player any ammunition. In fact, they are normally very difficult to keep alive.