Nagilum encountered the USS Enterprise-D in 2365. In the course of conversations with Nagilum, it called Humans limited, apparently because they were mortal, and it wished to perform experiments on them. It was interested in the concept of "death" and killed Ensign Haskell simply to witness the effect on him. After this it decided to study this aspect of humanity on numerous levels, proposing to kill a large portion, from one third to one half, of the ship's crew.