Fishing with Thursday

I went on a fishing trip with Thursday, the plan was to catch a dragon. Altough we didn't catch the dragon there we a lot of other fish to eat. It was mostly a calm trip, but after a few days we did notice some undead on both sides on the river. They were scared of by a Thunderwave of Thursday, but then suddenly some large creature attacked us from beneath the water. Thurday ordered me to use my heartstone to get back to Rosewood, while I was doing that he gave me a token and explained that it was magical and it could tranform in a boat if I needed it to. I don't know what happend after that.