Isaac McDougal

Isaac McDougal, also known as the Freezing Alchemist, is an original character exclusive to the 2009 series, Fullmetal Alchemist: Brotherhood. Specializing in water-based alchemy, he appears in the first episode as a former State Alchemist in the military who is currently trying to destroy Central. After killing a few soldiers with his water alchemy, he activates a transmutation circle to create a large amount of ice. He is then confronted by Edward and Alphonse Elric, and (after confusing Alphonse for Edward and accidentally making fun of Ed's height) is defeated and handcuffed. He quickly escapes after creating steam from a puddle as a diversion.

He later goes to prison to try to enlist Solf J. Kimblee in his plan to destroy Central, but is unsuccessful. Returning to the city, he encounters Roy Mustang, and quickly escapes him after dousing him with water. He makes his way back to the alley he originally started at and activates all the transmutation circles around the city, creating a giant wall of ice traveling towards Central. Al, Ed, and Alex Louis Armstrong all try to stop him but are unsuccessful. However, once Al and Ed get the upper hand in close combat, he is knocked off and is seriously injured. In desperation, he uses his blood as a weapon to distract the Elrics so he can get away but not before defiantly yelling out that he was trying to save the country. After turning down an alley, he confronts Führer King Bradley who, with a slice from his sword, kills Isaac.

He is also mentioned in Episode 2 during a report by Colonel Mustang, and is seen again in Episode 30 during his time as a state alchemist in Ishval. In Episode 35, Ed remembers about him and understands that he was aware of the secret plan of the Military. In Episode 50, while mocking the incompetence of Central Headquarters' forces fighting against Roy Mustang's coup d'etat, Major General Olivier Mira Armstrong mentions that she once heard that in the past, one rebel was enough to immobilize the entire Central Headquarters, presumably referring to Issac McDougal.

Water Alchemy
As his title indicates he is also able to freeze any source of water, even sources with water essence in them, allowing him to use any available source of water for a variety of feats such as paths to walk on or forming crude weapons to strike at his opponents with. As a last resort attack he can also freeze his own blood so as to strike his target. Contrary to his title, McDougal is capable of more than freezing. and upon touching a target he can boil the water so as to create a thick cloud of vapor so as to make his escape. By touching his opponent, he can freeze or boil the water in their body to instantly kill them; however this technique is ineffective when not used on flesh, such as Ed's automail.

His most powerful technique involves writing several transmutation circles around Central in a formation similar to the design of his transmutation. With this formation the large amounts of ice that can be created from the transmutation circles are apparently endless as not even Mustang's flames were able to subdue this attack. Destroying the transmutation circles are the only way to disable this technique, which also proves difficult as the ice buries them endlessly. As of episode 2 it is hinted that his abilities are linked with Alkahestry, which would explain how he was able to perform this attack while standing in the ice he himself created, and after destruction, recreate itself. To quickly access his alchemy, Issac has embedded his transmutation circle on his gauntlet and tattooed it on the palm of his hand. His circle consists of a point within a circle with two curves around them with make contact with the borders of another circle and two lines coming from the center touching the borders, resembling an eye with a line across and a text on an external circle. During his brief appearance, Isaac also demonstrated considerable agility and combat prowess, able to fend off both the Elric Brothers and dodge Alex Armstrong's assault.

Trivia

 * Though having a short appearance in the show, he hints at the supposed evil activity of the Führer and the Military, possibly already knowing that Bradley is a Homunculus or that they were just using Amestris as a Transmutation Circle. The latter is more likely, considering that he attempted to kill the Führer using mundane means.
 * Isaac and Lyra (from the 2003 anime) both share a similar Transmutation Circle. Due to their similar style, they might have the same ability of freezing, due to Isaac freezing water and Lyra chilling the air around her.
 * In the manga, there is a scene where Riza Hawkeye mentions the name of a man named Isaac, who is never seen. In the same scene during the anime, the man's name is changed to Ian, possibly to avoid confusion over this character and the unseen one.