There's a bug, i managed to use the potion on the lake and summon Derrida, but i never recieved his story as despicted in the walkthrough and i ended up stuck.
there is this possitive bug that if you win a battle and press go while the screen is still reverting to travel mode you will skip any confrontation that happened in between
 "The Trader of Stories"){kind=icon}
 "Frontier"){kind=icon}