This level is actually short but has the first boss which Duke must defeat. With Duke Nukem teleporting into the room, there is a grenade launcher conviently nearby as well the ammo of that weapon. This is useful for the boss. The Boss won't attack until you finally approach it. The boss is a massive green demonic-looking torso with mechanical stubs where its arms should be.
The boss attacks by spawning slimes from its mouth, as well as a very short range blast of steam from its stubby hands. To defeat it, arm yourself with the grenade launcher (if you not have done so) and try to lob the grenades into the back of the neck. Be careful though, in order to throw the grenades at its weak spot, you must be close due to the steam blasts from its arms. Do this 5 times which will result in blowing up the creatures head. With the beast killed, you can now pass it and head to the elevator on the other side.