ChipFTAC01 said:
Per one of the now non-canon Zahn books (I think that's which ones it was) some dark Jedi fled to dagobah and met an untimely end. Luke theorized that Yoga went there to hide because the dark jedis impression on the force countered out yodas presence. Sort of a force camouflage.
Right, Luke theorizes about the dark side cave shielding Yoda when he revisits Dagobah in "Heir to the Empire". He finds a ship's beckon call in the swamp which serves to get him to Lando's place in this plot, but then it is explained much more thoroughly in the late 90s "Hand of Thrawn" duology where Talon Kardde tracks down his former smuggler boss/mentor Jorj Cardas. Cardas tells a story of being on a freighter during the Clone Wars that was hijacked by a "Dark Jedi" who kills everyone on board but him for unknown reasons. The Dark Jedi eventually lands on Dagobah trying to escape the forces pursuing him and Yoda is there waiting for him.
They have a fight that lasts most of a day, with Yoda finally killing the Dark Jedi and then using the Force to nurse Cardas back to health, a process that allows Cardas to imbue some Force powers, mostly seeing things before they happen. He goes back home and becomes the most powerful smuggler outside of the Hutts, then the power all leaves him, and he thinks he's dying so he goes back to Dagobah, threatens Yoda with his blaster and his ship's weaponry (thus the beckon call) and Yoda embarasses him and tells him he waste his gift, and sends him off to find some random monks that live beyond the outer rim. The monks teach a different version of the Force use, but one that is rooted in humility. Yoda tells Cardas he can't heal him a second time because he's preparing to train his most important student of all time (Luke).
And yes, I did that all from memory.
