In this chapter you will find useful advice that will make the battle much easier.
Details can be found in separate sections.
Before the battle
This opponent is rather easy to defeat. However, you must notice one limitation related to this battle. If you lock the camera on the opponent, it will remain focused on his head which during most of the fight is unavailable for you or attacking it is very dangerous. You should make a habit of positioning yourself in such way that you will be able to hit opponent's abdomen. One of the important things related to that is using the medium stance which will enable you to hit everything in 180 degrees around the camera position.
The opponent is very slow and his attacks are easily predictable if you learn to control the camera during this fight. Additionally, the arena is very large and you can take advantage of that. However, keep in mind that despite the fact that the opponent attacks very slowly, he has similar movement speed as you. Because of that, you can't escape too far from him.
Before the fight you should equip some decent armor and take the maximum number of antidotes. You will find a few of them on the battlefield if you require additional resources.
Try reaching the back segment of opponent's body once the battle fight and destroy the pieces you manage to reach. What's important, the health bar of the boss is related only to four segments counting from the head. The rest is a separate entity.
You shouldn't have trouble with destroying a few segments, but you must know that it is related to a kind of trap. After destroying the segments at the end the creature will stick only to a few front segments mentioned earlier. The remaining ones will escape on their own, but one of them will stay and start generating the poisonous fog. If you won't find and destroy it quickly, the arena will quickly become filled with poison.
Don't run the escaping parts of the centipede, but focus on finding the piece that stayed. After reducing the length of his body, the boss will become much faster, but his attacks will remain slow. At least the ones performed when his head is close to the ground. Observe the behavior of the boss and frequently attack him from behind.
The opponent will leave the battlefield once you reduce large piece of his health bar. Following him is pointless. Instead of that, you should regenerate your health or enchant your weapon while he isn't nearby. After a while he will return will all his surviving segments attached back to him. You can finish him immediately or destroy all the segments once again. Opponent's attacks are easy to predict and if you quickly destroy the piece of the boss that creates the poison, he shouldn't threaten you.