Tim Marcoh

Tim Marcoh (ティム・マルコー), formerly the Crystal Alchemist (結晶の錬金術師, Kesshō no Renkinjutsushi), was the leading researcher in the military's Philosopher's Stone creation project.

The Ishval Extermination
After sacrificing a number of innocent Ishvalans during the Ishval Civil War to create new stones in Laboratory 5, he fled the military with some imperfect stone samples. He settles down in a small country town where he uses his stones to heal the sick under the identity of "Doctor Mauro".

The Cruel Research
He is later found by the Elric brothers and Alex Louis Armstrong, who demand information about transmuting living things. At Marcoh's house, he threatens them with a gun but Alex calmed him down. Marcoh eventually explains that he left the military because he couldn’t continue doing research that had been used to kill during the civil war. Marcoh revealed that his research is the Philosopher's Stone shocking everyone around him.

Marcoh showed it to them in it's liquid form instead of an actual stone and notes that this is imperfect and can become unusable. Edward knows that this can be perfected and wants to see the research materials, but Marcoh initially refuses because he sees this as evil research. He makes them leave, however he has a change of heart and delivers a note to Edward at the train station stating that the research materials are hidden at the National Central Library’s 1st Branch. When Marcoh then returns home, he is shocked to find Lust who is waiting for him.

Imprisoned and a Meeting of Fate
After found by the Homunculi, he is kept under house arrest, forced to stay put and alive or risk the destruction of his town. He is later taken into their custody to be used in their future plans, and is kept locked up deep below Central. When Envy visited Marcoh, Marcoh questions Envy by speculating that their plan is to use the country and it's people to make a giant transmutation circle in order to create a Philosopher's Stone which Envy admits that he is close and on the right track. Afterwards, Envy takes great pleasure in tormenting Marcoh by constantly reminding him the Homunculi would massacre his hometown if he ever escaped.

After some time as a prisoner, he is found by Scar. Recognizing Scar as a means to his end, he reveals the Ishvalan of his involvement in the Ishval Civil War in the hopes of being killed in vengeance. Scar is overcome with rage over Marcoh's revelations, but first demands that the doctor explain exactly what was going on with the eradication of his people.

Marcoh tells Scar everything he knows about the Ishval War, including the involvement of the State Alchemists as "Human Weapons" and the fact that the Philosopher's Stone that he himself had created was crafted using the bodies and souls of living Ishvalan war prisoners. When Marcoh's story ends, Scar flies into a rage at what he has heard, but informs Marcoh that he will not be allowed to die so easily for his sins. He demands that the doctor reveal all his knowledge regarding the State Alchemist known as Solf J. Kimblee as well as aid him in deciphering the more confusing parts of his brother's research notes - citing his brother's assertion during the war that something about Amestrian alchemy did not make sense. Taking Marcoh's clothes and the body of a small guard chimera chained up nearby, Scar and Marcoh transmute a false corpse which the Ishvalan serial killer deconstructs to simulate one of his grisly murders while scrawling "Vengeance" on the wall in blood to make the scene more convincing. Then, using the duct system, the two escape to the surface where Scar regroups with Yoki and May.

May is surprised to learn that Marcoh had created the Philosopher's Stone - the key to immortality - but Scar informs the little girl that such an evil thing should never be coveted. Despite the fact that Marcoh has joined their party, Scar calls the man his enemy and promptly unleashes his deconstruction alchemy on the doctor's face, disintegrating his epidermis, before asking May to use alkahestry to only staunch the bleeding rather than heal the wound - as it will be more convenient to have Marcoh's face disfigured so as to keep the Homunculi from recognizing him. He then declares that they will be heading to the northern region of the country - to the place where he had hidden his brother's research notes.

Answers in the North
While Scar and Yoki attracts attention and distracts the military and Kimblee, Marcoh travels with May Chang to the north. The two of them come upon the Briggs Mountain Range and remark that they should be nearing the location that Scar indicated on his map.

Arriving at Scar's specified location, Marcoh and May uncover a small, buried box inside of which lie the notes left by Scar's brother on the fusion of Xingese alkahestry and Amestrian alchemy. Wondering whether this information will bring about hope or despair, Marcoh and May get to work deciphering the code. When they finished deciphering it, Scar and Yoki returns and told them that the Briggs soldiers found their location so they have to move to another location (most likely Baschool).

In Baschool, Marcoh and Yoki were searching for May (who heard Alphonse's voice). When Marcoh found May along with the Elric Brothers, he is shocked to see them again. After Scar was captured, Marcoh and May arrive on the scene and explained that they still require Scar's help in deciphering the crucial alchemical notes left by his brother. Marcoh, Scar, May, Yoki, Winry, Jerso and Zampano are heading to Fort Briggs by using Baschool's underground mining tunnels as their escape route. After they exited the tunnels, they found Alphonse in the thick snow who delivers the bad news, that Central's forces have occupied Briggs with Major General Armstrong having been summoned to Central Command. As the group talks where to head off to in order to hide, Scar suggests the nearby town Asbec where some of his people are hiding and leads the way.

The Ant's Bite
When Jerso and Marcoh gathering some firewood, Zampano arrives with the disguised Envy, and Envy reverts to his normal form as he prepares to catch Dr. Marcoh. To his surprise, Envy is caught in an alchemy trap with snow transmuted into ice spears. Zampano and Marcoh make it clear they lured Envy and Marcoh admits he set special traps in the snow that detonate only for Homunculi as Envy gets attacked by more ice-related transmutations. Unbeknownst to Envy, this is actually May using alkahestry, with their transmutation symbols buried underneath the snow.

Angered by the fact of being mocked at, Envy transforms into his giant form and tries to crush Dr. Marcoh with his tail, but Jerso in his chimera form saves him, followed by Zampano striking Envy in his right eye with the quills from his chimera form. After May creates a large number of ice spikes to trap Envy, once Envy breaks free, Scar jumps onto Envy's back to finish him off with his decomposition technique. However, Envy is still alive and grabs Dr. Marcoh with his tongue, ordering everyone to stay put or he will kill him. Envy taunts Dr. Marcoh and states he will eliminate Asbec as punishment for his betrayal, or capture the villagers and use them to become Philosopher's Stone ingredients just like what was done with Marcoh's former workers which reside as Philosopher's Stones now. Surprised by this, Marcoh admits to Envy's statement that while he knows how to use human lives to make them into Philosopher's Stones better than anyone else, he also knows how to destroy them. Using a hidden transmutation circle on his right hand, Marcoh attack's Envy's Philosopher's Stone, causing a giant power surge, to which the Ishvalan villagers, Yoki, and Winry can see in Asbec. Envy's giant body disintegrates as Zampano pulls Marcoh away from it and his human body emerges while being still attached, shocked and appalled that this is happening to him. As Envy yells at Marcoh and the chimeras not to look down on him, a small, green slug squirms from the husk and the body disintegrates to bits.

After the battle, Winry demands to know why Marcoh was acting so reckless. Marcoh admits it was for the first time of settling things on his own accord, rather than doing what he was told similar to Winry's parents just as Envy bites Yoki's finger. His attempt to control Yoki's body to use as a hostage fails as no one in the group considers Yoki to be their friend and Marcoh admits they'll kill both him and Yoki if he gets out of line and Al pulls Envy off of Yoki's body as Marcoh admits he was bluffing much to Yoki's annoyance. Afterwards, Scar announces that he'll be heading out on his own mission to search for something that can help change Amestris, despite his grudge for what happened in Ishval and that he'll need Dr. Marcoh to accompany him which he agrees. Before the Promised Day, Scar and Marcoh head east across the Great Desert as a start of their journey to gather Ishvalan comrades from all over the country.

The Promised Day
In Reole, Scar and Marcoh, who have just returned from their travels encounter Zampano, Jerso and Yoki who waited for them and they have now decided to head together to Central City. Their party is met in the forest by a large group of Ishvalans, including Scar's Master, and Scar explains that he and Marcoh have gathered a fair number of like-minded comrades over their long journey.

In Central, Scar, Marcoh, Yoki, Zampano, and Jerso learned from a group of homeless men that May Chang and Xiao-Mei haven't returned to Xing yet and have been spotted nearby and also learn of the train incident involving the Führer, which shocked them. Afterwards they headed to the Elrics' group and shocked at looking Pride's dome prison.

When the coup d'etat at Central begins, Marcoh, Yoki and Heinkel stayed behind. Later, after Kimblee springs Pride from his dome prison, Marcoh takes part in a ruse to deceive the two along with Heinkel and Alphonse. Alphonse gives Marcoh the Philosopher's Stone that Heinkel gave him, which he then used to heal Heinkel's wounds while Alphonse acted as a diversion. When Pride was about to kill Marcoh, Yoki unexpectedly arrives in a jeep, which deflects the attack and knocks him down, which also frees Alphonse in the process. Afterwards, Yoki, Marcoh, Alphonse and Heinkel escaped from Pride and headed to Central.

New Beginnings
He is last seen with Dr. Knox, telling Colonel Mustang that he will use the Philosopher's Stone to give him his eye sight back on the condition that he improves conditions for the Ishvalan people, restores their homeland, and allows himself to stay there as a doctor, to which the Colonel accepts.

2003 anime
In the first anime series, Marcoh plays a significantly lesser role. After being taken into custody by Juliet Douglas, he is confronted by Lust. She questions him about the information he gave to the Elrics and subsequently murders him. His body is implied to have been eaten by Gluttony.

He later makes a brief cameo in the penultimate episode as one of the forms Envy uses to toy with Edward.

Abilities
Dr. Marcoh is one of the oldest known alchemists of the series and as such has incredible knowledge regarding alchemy. His most notable knowledge is related to the creation of the Philosopher's Stone, knowledge given to him by the homunculi. After numerous experiments with their creation, he is also able to destroy them, an ability which proves effective when fighting Envy.

Due to his elderly state, Dr. Marcoh is not able to use alchemy in combat, but rather he proves to be skilled when it comes to support tasks such as healing or deciphering codes. He is also very skilled in medicine, as more than one person has asked for his assistance, although his healing abilities may be possible through the use of the Philosopher's Stone, rather than a unique ability like Alkahestry.

What his epithet as the "Crystal Alchemist" means is unknown, but it is likely connected to the Philosopher's Stone in some way.

Regardless of his inability to fight, his knowledge makes him a valuable ally.