Story related. The first boss you will encounter very early in the game.
*** Spoiler - click to reveal *** A giant octopus at the end of the first dungeon. This easy boss has two different kind of attacks. It will try to hit you with its arms or throw jars at you. Both attacks require the same strategy. Keep moving around , hit the arms with your sword , roll away and chase the arms again and hit them. Never stand still and keep moving. When you have destroyed a couple of arms his head will start to float and you can do MAJOR damage by hitting his yellow mouth. The second part of the fight will be the same , hit the arms until his head starts to float , hit his mouth and that will be the end of the first boss in this game.