The Rotten

The Rotten is a boss in Dark Souls II.

The Rotten is located in Black Gulch. The Rotten is a huge mass of undead that have fused together, forming a single creature. After seemingly being unable to put the head of a statue back on its body, he becomes enraged and proceeds to focus his attention onto the player. The Rotten's attacks are quite damaging and can send the player flying.

Lore
DaSII=
 * -|SotFS (Spoilers)=The Rotten was once named Gryth, king of Shulva, Sanctum City and guardian of Sinh, the Slumbering Dragon. Sinh was an ancient, sleeping dragon who was discovered by the people of Shulva and subsequently worshipped. Gryth built the city itself around Sinh's resting place, and created Eternal Sanctum to protect the dragon from intruders.

Sir Yorgh and his powerful Drakeblood Knights eventually mounted a siege and invasion of Sanctum City in order to defeat the dragon and steal its fresh blood, which they believed granted a true understanding of life.

After defeating the Gryth, Sir Yorgh and his knights pushed into the bowels of the Dragon's Sanctum where Sinh slept. Using his spear, Yorgh pierced Sinh to claim its blood. Sinh immediately awoke and expelled a poisonous fog built up over the ages and completely wiped out Sanctum City, covering it in toxic poison. Gryth was consumed by the poison and transformed into The Rotten, but legends remember him as the Sunken King. Now he watches over the discarded and abandoned in his sanctuary deep under the ground.

Summoning

 * Lone Hunter Schmidt can be summoned for this battle outside the boss fight underneath the Giant shortcut.
 * Lucatiel of Mirrah can also be summoned in the Hidden Chamber bonfire room, but only after speaking to her beforehand. She can physically be found by falling off and landing on a ledge just outside the first bonfire; use a torch to see the ledge clearly. After falling down, follow the path to her – it also leads to the raised area with the poison-spitting statues. The ledge that one falls on should not be confused with the later ledge that has a door that can be opened with the Forgotten Key (that leads to Darkdiver Grandahl) and the two Giants.

Fight Overview
Throughout the fight, The Rotten will alternate between using his cleaver and using his empty hand. His cleaver deals heavy damage and can send the player flying or easily stunlock the player and break their guard. The hand has two moves; a frontal smash and a grab (the grab does more damage). The grab does damage twice; the initial damage is from the grab itself and the second portion of the damage comes when he wrings the player out like a rag.

Strategy
During the fight, players would do well to avoid the flaming patches throughout the arena as they deal heavy damage over a short period of time.

The Rotten attacks with his cleaver by performing a heavy downward slash, two quick downward slashes followed by a third heavy slash with slight windup, or horizontal slashes. Dodging toward his right side is a good idea as the player risks being hit by the blade by rolling away from him toward the left.

At 50% health, The Rotten will begin using magic attacks that deal heavy dark damage. One travels in a straight line after a heavy downward slash, while the other is an AoE attack. He will be vulnerable for a short time after each attack, giving ample time to switch to offense. With the Old Leo Ring and a thrusting weapon equipped, this fight can end very quickly soon after.

Hitting either of his arms (easier to do with a weapon that has vertical swings) a few times will sever it, but it will regenerate after some time. If the player manages to cut one of his arms off, there is a chance that it will drop a Lockstone.

With magic, the player should keep their distance from The Rotten and should only cast one to three spells depending on which attack The Rotten used.

Attacks
Knife Slam: Slams his knife on the ground.

Swipe: Swipes his knife in a wide arc.

Combo Slam: Slams his knife on the ground twice in a row.

Arm Slam: Uses his other arm and slams it on the ground. Blockable, but completely drains stamina.

Dark Aura Explosion: Charges up with a dark aura emitting around him and explodes in an AoE radius.

Dark Knife Slam: Slams his knife in the same matter of the knife slam move, then fires off a dark attack from the knife while in the ground.

Grab: Grabs the player with his other arm, then twists the player with both hands in a towel-drying manner. Unblockable, and inflicts heavy damage.