system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] What is the dark side cave on Dagobah?

I have rewatched The Empire Strikes Back and played The Force Unleashed 2, and still have confusion about the Dark Side cave Yoda talks about. What is it? What is it's potential? And what has other people seen in the cave?
gpt
It is the site where a powerful Dark Jedi died. The abilities of the cave are the result of that Jedi's Force Echo, basically the same technique that allows for the existence of Force Ghosts, in a more abstract form.