While this boss may seem easy on the easier difficulties, in Hard mode this battle can prove quite difficult. The following are a few quick hints as to staying safe and taking off the most damage. First off, keep moving. Standing in place makes you an easy target for mines and earthquake, and you will often get chances to regain energy from the wires. Second, keep your shield up. This will keep you safe from ray attacks and will allow you to concentrate when damage can be done. Also, use your dodge roll to ensure you do not take damage from his blast. If the blast hits you, he will most likely quake immediately after and very close to you. This will only add insult to injury and leave you at near death. If you find you will be caught by a quake, try to run out of the arena. You will be snatched and thrown and suffer no damage from the quake or fall. Later in the fight when Kessler quakes and his echoes appear, try not to worry about them. If you continue to move as advised, they will disappear before getting near. As for his robots, constant moving will keep their grenades at a safe distance and they can be picked off with ease and precision. The best way to damage Kessler is to use your fully upgraded grenades in between his ray attacks. After he completes one shot, drop your shield and throw one in the area he spawns. Note: His spawn points may be a few feet away from his previous spot if you are standing still in this phase. After one is thrown, quickly raise your shield and repeat. Grenades take off large chunks of health and will put him down rather quickly.