I have experimented quite lot with the minigame now. I have gone through the river, the swamp and the bridge. I have killed the shades, ghasts, and even the tentacle monster without getting my companion killed. It's hard, but not impossible. I even met the good event, that heals and blesses you. Here's the picture of the blessing. I had my strenght boosted, so that didn't come from the blessing. Oh, just got a yellow agility tome from a red token. Gave me 2685 agility experience.