When my son was two he went through a phase of intense nightmares, almost night terrors. He also spoke of monsters, from some cartoons, maybe even the Pixar film. Our solution was to have Daddy do a monster hunt, with a toy gun, in his room every night. Once the room was cleared, he would settle down to sleep, but we let him keep the toy gun (an empty one dollar watergun) under his pillow so that if the monsters came back, he could protect himself.
If you're opposed to guns, even toy ones, you can still try the ritual aspect of a parent chasing all the monsters out before bedtime and see if that helps.