To find this boss, make your way through the Forest of Fallen Giants, kill the Pursuer, and then use the bird's nest to get to the Lost Bastille. Counter-attack with just a single attack unless you have a weapon with a massive attack speed. Instead, dodge every attack you can, and keep your shield as a reserve for when you make a mistake with your timing.
You can't block all the time though, as you run the risk of running out of stamina if you do.
We've got a more detailed guide to the fight with the Rotten over at our boss fight page, but you should try to stick to the centre of the battle arena to avoid the worst of the fire-pit damage, and you'll also want a shield that blocks 100 percent of incoming physical damage. The Rotten awaits you at the very end of this area. Head through this region, then go through the Gutter until you're in the Black Gulch. You'll find the Rotten by travelling down the Majula well and then making your way through the Grave of Saints. If you're struggling to take him down, take a look at our complete guide to the tactics required in this fight.
You should also be able to dodge most of these attacks, so don't worry too much about equipping any damage reduction gear. The King likes to throw attacks at you in pairs, and so you should never be too quick to launch your counter-attack against him.
