Arthur Langtry

Arthur Langtry is a wizard and a member of the Senior Council. He holds the position of Merlin, and is referred to as such throughout the series. He first appears in Summer Knight.

Description
"The sentence is death. To be carried out immediately."

- The Merlin

The Merlin is tall and broad-shouldered, and has cold blue eyes. He wears his perfectly groomed, snowy white hair long, and has a long silver beard. His eyes are winter sky blue and alert, his features long, solemn, and noble. He wears a blue robe and a silver circlet about his brow, and his staff is of elegant pure white wood, completely free of any marking.

Ebenezar McCoy comments of him that: "as usual, he's half right half wrong, and all gutless." However, both Harry Dresden and Carlos Ramirez have stated that "You don't get to be Merlin by collecting bottle caps" when referring to his magical might and political mastery.

In Changes, when he and Dresden meet in the Warden's Worry Room the Merlin is dressed in simple white robes. He also wears something similar to a gunslinger's belt of white leather hung at his hips, looking somewhat like the tactical gear made for Special Forces operators. Multiple potions vials ride in individual leather cases, and the leather-wrapped handle of an anemic rod or a stubby wand pokes out of his holster. Several of the pouches are fastened closed, and look as though they contain bits and pieces of standard wizard gear. He also bears a long, white staff, a simple wooden pole made of an unfamiliar wood.

Abilities
The Merlin is one of the oldest and most likely the single-most powerful wizard on the White Council, and perhaps even the entire planet. He is a master of Wards and defensive magic, able to almost singlehandedly halt entire armies (who have magical capabilities of their own) with them on multiple occasions. He can also display some offensive power.

In Turn Coat, he demonstrates his absolute mastery of mental magic by telepathically communicating with everyone within the entire assembly simultaneously, providing differing instructions to them all about what to do during the Mistfiend attack, including specific instructions for Dresden to capture Samuel Peabody who is escaping. In the words of Dresden, the Merlin had "in the literal length of a second and a half, turned pure confusion into an ordered battle" because all of the instructions were delivered, complete with a mental image of the Speaking Room so that everyone could see in the dark, in less than a second.

Summer Knight
In Summer Knight, the Merlin holds a conclave including the entire Senior Council in Chicago. His intent is to put all blame on Dresden for The War with the Red Court, and get his wizard status revoked.

During the conclave, the Merlin tries to railroad one of his cronies onto the Senior Council in Pietrovich's seat, sans discussion so that he could control the vote. Martha Liberty calls for general debate, providing the opportunity for Ebenezar McCoy to get the position instead. The Merlin, Aleron LaFortier, and Ancient Mai then try to get Dresden stripped of his wizard status on the White Council, which would allow them to turn Dresden over to the Reds who would murder him. Later on, Morgan shows up at Dresden's apartment and tries to goad him into attacking; just in time, Dresden figures out that another wizard is waiting outside to witness Dresden attacking a Warden, and realizes that the Merlin had set up the entire thing to try to get rid of him.

Death Masks
In Death Masks, Ebenezar McCoy contacts Dresden regarding his duel with Paolo Ortega and informs him of the state of The War. He mentions that the Merlin won't allow the White Council to take offensive action against the Red Court, in an attempt to seek peaceful resolution. McCoy notes that the Merlin's "fancy wards" have successfully repulsed a major attack, and that the casualty rate for Council members in their homes have dropped to zero as a result of these Wards, with only a scant few Warden casualties during intelligence missions. However, McCoy still insists that the situation cannot last and that eventually the Red Court will grind away all of the White Council's allies until they are completely alone.

Dead Beat
In Dead Beat, Anastasia Luccio updated Dresden on The War. Luccio said that the Merlin went out into the field with the Senior Council, convinced to do so by McCoy. The Red Court attacked them on the Ways in Sidhe territory as they retreated with a great many wounded, with the Reds calling up Outsiders and demons to aid the assault. McCoy and Martha Liberty came to their aid, buying time for the Merlin and the Gatekeeper to erect a single massive Ward to hold off the entire army of Red Court vampires, demons, and Outsiders, allowing the Wardens to escape with the wounded.

Proven Guilty
In Proven Guilty, the Merlin is present along with Dresden and other Wardens at the execution of a Korean boy who had violated the Laws of Magic and caused horrific damage to his family. After the boy is killed, the Merlin and Dresden speak, and Dresden talks about his sorrow over the execution. The Merlin firmly tells him that the boy was incapable of rehabilitation and that there was no other way. He softens slightly at the end of the conversation, telling Dresden that it wasn't easy, but the Laws of Magic had to be obeyed.

At the end of the novel the Merlin reappears for the trial of Molly Carpenter. With most of the Senior Council on assignment without designated proxies, the Merlin holds 6 of 7 votes, with the Gatekeeper being the only odd vote. Dresden calls upon the sympathy of the witnesses, showing them Carpenter's face and talking about learning from mistakes. He wins the room, but as soon as he looks at the Merlin he realizes his mistake; he had undermined and insulted the Merlin, using the trial as a direct challenge without accommodating the Merlin's image and ego. The Merlin responds by acknowledging the unfortunate nature of the situation, but declares that he is unwilling to take chances with the war against the Red Court going so badly, and orders her immediate execution.

Before the sentence could be carried out, the Gatekeeper stalls by deliberately not voting, because although his vote would be irrelevant in either case, he is entitled to vote nonetheless. The Gatekeeper successfully stalls until the rest of the Senior Council arrives with Michael Carpenter, Molly Carpenter's father, who had just saved all their lives and the lives of dozens of younger wizards in battle. Dresden quietly points out to the Merlin that as Michael had saved plenty of their lives, the Merlin could at least save his daughter. Dresden also adds that there's no downside; if Dresden is right, they get a talented wizard, and if he's wrong, they can still execute Carpenter. The Merlin agrees, but adds a threat by noting that if Carpenter is killed, Dresden will die too.

Turn Coat
In Turn Coat, while Listening, Dresden learns that the Merlin is the one pushing Joseph Listens-to-Wind to perform the ritual to find Aleron LaFortier's real killer. Samuel Peabody takes Listens-to-Wind away for signatures, and Dresden approaches him, offering help in exchange for copies of Morgan's file. The Merlin's only condition to accepting this deal is that Dresden find the traitor, the real killer, not simply prove Donald Morgan's innocence.

During Morgan's trial, the Merlin presides over the hearing in the Speaking Room until Wizard Peabody is identified as a traitor, causing Peabody to release a Mordite-imbued Mistfiend into the room to provide a distraction for his escape, resulting in the deaths of many wizards in attendance. In response, the Merlin telepathically marshals the White Council to action against the Mistfiend and dispatches Dresden in pursuit of Peabody, resulting in the death of Peabody and rapid containment of the Mistfiend, saving countless lives.

At the end of novel, Aleron LaFortier's supporters claim that the Merlin ignored their safety and was negligent with security. The Merlin decides to allow rumors saying that Morgan and Peabody conspired, feeling that it was better to appear to have acted with deadly strength and power. As a result of the Merlin's decision, this also allows those behind Peabody to know that the Council killed an innocent man and one of their largest military assets. The Merlin also asks Klaus Schneider to decline the Senior Council seat, so that it could go to Gregori Cristos, who threatened that he and all of his allies would secede if he didn't get the seat.

Changes
In Changes, Dresden sees the Merlin in the Warden's Worry Room. The Merlin doesn't buy into Cristos' public show of currying up to Arianna Ortega for peace with the Red Court, but a great many wizards on the Council do. To deal with the situation, the Merlin puts up a pretense of supporting Cristos while his own plot to destroy the Red Court is in the works, demanding that Dresden play along. He impresses upon Dresden that one child is not worth the lives of billions, although Dresden disagrees, saying that the Merlin has it backwards — that "no life is worth less." Confounded, the Merlin subtly threatens Molly Carpenter with his eyes in order to completely dissuade Dresden, and so Dresden departs.