Sinh

Sihn, also known as the Slumbering Dragon, is a major antagonist in Dark Souls II, appearing in the Crown of the Sunken King DLC as the final boss.

Biography
Long ago, the Sunken King erected the underground city of Shulva to worship Sihn, an ancient dragon known for his poisoned-infused flames and resting. Although knowing Sihn would become hostile immediately upon waking up, the Sunken King found a way to preserve Sihn by forcing him to perminately sleep. Priestesses were established to sing in rituals to ensure that Sihn would remain asleep. Then one day, Sir Yorgh, the leader of the Drakeblood Knights, invaded Shulva to obtain the blood of Sihn, believing it would bring an understanding of life. Defeating the guards, Sir Yorgh and his men engaged Sihn, waking him up from the years he rested. A massive spear was impaled through Sihn's chest, unleashing the poison that built up inside him. A poisonous cloud covered the entire city, killing everything in its path. The survivors who resisted the miasma were mutated into poisonous hollows.

When the poison exhumed, Sihn returned to his rest. Elana, the queen of Shulva, used multiple souls and her own songs to keep him asleep, believing that once he returned to his powerful state, she can use him to claim her revenge. When the player enters Shulva through the Black Gulch bonfire, Sihn can be found near the first bonfire resting. As the player approaches, Sihn prematurely wakes up, aware of the player's presence. He lets out a roar before flying off. Later when the player walks towards the Dragon's Sanctum, Sihn attacks the bridge with fireballs as they begin to cross it, killing the two Sanctum Soldiers on it. He would then return to Dragon's Rest.

After killing Elana, the player unlocks an entrance from the alter that leads to Sihn's arena, where he emerges from the rocks to engage the player. For a big opponent, Sihn can move around the arena fast using his feet or wings. He attacks by biting when the player is near his head, stomps when they are underneath or beside him, and swinging his tail when they get behind him. Sihn can also lift off into the air, diving towards the player. He can also spew out fireballs at the player, leaving behind poisonous mist that causes quick toxic buildup. His skin has a corrosive effect, causing the player's weapons to greatly lose durability. Despite his brute strength, Sihn does have a weakness; targeting the wound with the spear exposed from his chest deals high damage compared to hitting Sihn elsewhere. Once Sihn is defeated, he drops his soul and the Crown of the Sunken King, which reduces vigor and vitality to increase strength, dexterity, endurance, faith, and intelligence.

Trivia

 * Sihn's tail can be cut off to prevent him from using any tail attacks. Unlike other dragons, cutting it off will not make him drop any rewards.
 * Not only does Sihn resist fire and toxic attacks, but he is also resistant to lightning attacks, which is odd since most dragons are weak to lightning.
 * Like how Black Dragon Kalameet's name is a play on "calamity", Shin's name is a play on "sin".
 * Sihn takes more damage when the player faces him solo.