Hello
No you can't kill the robot

Here are the emplacements of the four keys:
1- Skeleton trooper at the entrance (I suppose you got this one)
2- Closed room at the top of the map (you already got this one)
You have to lure the robot between the two daemon heads. Use frost spell, forcefield or the stun ray (found in the upper level) to freeze him the time you get inside the room.
3- Lower right of the map, after the room with the timed trapdoors (I also guess you've already found this one, it's in an alcove)
4- The last one is deeper underground. You have to jump in one of the button-controlled traps in the room with the wraith
Have you solved the riddle "He watches your back?"
Until next time!
Khollik