The Rotten

The Rotten, formerly known as Gryth or the Sunken King, is a major antagonist of Dark Souls II. Once the king of Shulva, he was revived as an abomination of merged hollow flesh given life by the soul of Gravelord Nito, expanding his immortality by forcing hollows to join his hive mind.

Biography
Back when Gryth was still human, he lead the people of Shulva in worship of Sihn, a slumbering dragon beneath their town. One day, Sir Yorgh and the Drakeblood knights raided the city to claim the blood of Sihn. Gryth tried to fight back and was killed by Sir Yorgh. After Sihn released a toxic fume that suffocated the city, Gryth's body found itself in the Black Gulch, a dark and decrepit cavern below Majula filled with hollows and monstrosities. At some point in the past, Gryth was resurrected as an entity born from an amalgamation of numerous hollows merged into each other held together with chains and a cage-like head, known as the Rotten.

As the Rotten, Gryth collected multiple souls of life forces to sustain his immortality, eventually possessing the Old Dead One Soul, a part of the Death Soul once held by Gravelord Nito. It became the leader of the Black Gulch, granting those who lose their way into his "sanctuary", by merging them into him by force. He also placed multiple statues in the area that spit poison at intruders. When the Bearer of the Curse enters the Rotten's "sanctuary" hideout, he can be seen building more of the statues. One of the statue heads fall off, angering the Rotten enough to smash it. He then notices the player and roars at them.

The most important thing to take notice of while fighting the Rotten is the area, as there are multiple fire pits around the sides of the arena. The Rotten can use these pits as an advantage to get the player stuck. While a slow opponent, the Rotten's attacks deal heavy damage should they hit the player. He uses a large knife as his weapon, which he can swing around. He can use his other arm to slam the player or grab and throw them. He can also spit out an oil-like substance that when doused and exposed to one of the fire pits, the player will combust and lose a chunk of health. The Rotten can also emit himself in a dark aura to explode in a radius around him. Defeating the Rotten reveals a Primal Bonfire.

Trivia

 * An unused description for the Rotten's soul reveal its origins as Gryth.
 * The large hollow on the Rotten's left shoulder appears to be the brains behind the Rotten's hive mind, shown as it mimics the movements of the Rotten's arms. It is unknown if it was Gryth.
 * In New Game Plus, the Rotten drops the Old Dead One Soul.
 * Cutting off the Rotten's left arm makes it drop a Pharros' Lockstone.