Darkeater Midir

"Midir is his name, and the Archdragons are his forebears. He once railed against the dark, but was by dark afflicted. Now here, returned, he remaineth. To watch over the sleeping Princess, true to the old accord...And yet, I would have thee put the dragon to rest. Afore the dark consumeth him, and his vows are forgot."

- Shira telling the Ashen about Midir.

Darkeater Midir is a major antagonist and optional boss in "The Ringed City" DLC for Dark Souls III. Trained by the gods as a guardian of the Ringed City, the dragon was corrupted by the Abyss and became an adversary to the residents of the city.

Biography
A descendant to the Archdragons that Gwyn and the kingdom of Lordran fought off to start the Age of Fire, Midir was raised by the gods as a guardian of the Ringed City from outside threats, particularly the Abyss created by Manus. Granted with immortality, Midir continued his duty of fighting the Abyss' spread long after the gods perished. However, his eternal battle with the dark would taint him with the same Abyss he fought, turning him hostile against the residents and the Spears of the Church, the guardians of Princess Filianore. When the Ashen One is summoned to the Ringed City, Shira requests them to slay Midir before he becomes fully consumed by the Abyss.

Midir can first be seen flying off not long after entering the Ringed City. He will not be interactable until reaching a bridge past the abyssal swamp. He will sit on a cliffside for the player to cross before swooping down and ingulfing the entire bridge with flames (there are rocks that the player can hide behind), doing so until the player reaches the Shared Grave area. Immediately after walking out will Midir land on the bridge leading to the Church of Filianore, blocking the path. While the player can quickly run to the building and avoid Midir's flames, hitting him enough times staggers him. Striking Midir with a visceral attack to his head will make him lose his grasp and plummet to the bottom. In the Church is a secret room found past the illusion of a Black Knight with no sword. Behind the altar is a large hole that leads to an underground chasm, with the injured Midir in the middle. Approaching him will wake him up and begin his optional boss battle.

Midir is a very difficult enemy to take down due to his high health and agility despite his massive size. Like other dragons fought in the Dark Souls trilogy, Midir tends to use his mouth to bite the player when they are in front of him, swipe his claws when they are at his side or under him, or swing his tail when they are behind him. When at a distance, Midir breathes flames that cover a majority of the arena, one of which turns into a dark laser that deals extremely high damage to the player. The best strategy is to prioritize attacking his head as it takes the most damage compared to the rest of his body. When Midir stands up to breathe fire underneath him, quickly run between his legs and strike his tail.

Once Midir has roughly half of his health left, he will start channeling Abyss magic into his attacks, starting with a large explosion surrounding him. He can also summon large humanity orbs to chase after the player, similarly to the Affinity spell. His most dangerous move is an even larger and more powerful dark beam that covers most of the arena, creating a series of explosions that deal massive damage, enough to potentially kill a player at full health. But after using it, Midir temporarily pauses to catch his breath. Like other large enemies in Dark Souls III, hitting Midir enough times staggers him, allowing the player to use a visceral attack on Midir's head to take out about 15% of his health.

Once Midir goes down, alongside his soul he drops the Spears of the Church; equipping it as a ring recruits the player to the Spears of the Church covenant.

Trivia

 * Midir's name is a play on "murder", similar to how Kalameet is a play on "calamity" and Sihn on "sin".
 * Shira will give the player a Titanite Slab after defeating Midir, but only if Halflight had not been killed yet, as she will then become hostile.
 * Using the Chameleon spell or a Young White Branch in Midir's arena turns the player into a Humanity Phantom.
 * All the damage the player deals to Midir on the bridge will not be carried over to his boss battle.
 * In Midir's arena are multiple corpses. Either these are people who failed in slaying the dragon, or the Spears of the Church had been using sacrifices to soothe the dragon's wrath.