This may sound stupid but I cannot figure out how to get the tree to attack so I can get to the island. I know the knife has something to do with it. I think a walkthrough does need to be done as a lot of my progress is more or less due to trial and error. Either that or increase the amount of npcs giving hints.
Actually, there's some point in the game where you meet a special character, which gives you more hints if you talk to her. You can find that character by travelling between the two furthest planets.