Tom

Thomas, known simply as Tom, was a blacksmith in Camelot and is the father of Guinevere and Elyan. And he is mentioned throughout the series. He was one of the victims of the disease spread by Nimueh and her Afanc through the water system. Merlin used his magic to cure him but unfortunately, Gwen is accused of sorcery. Merlin, Arthur and Morgana save her by killing the Afanc. He shortly appears after when Gwen is released and reunited with her father. (The Mark of Nimueh)

When Tristan de Bois is raised from the dead Gwen stole one of his sword's and gave it to Merlin who imbued the sword with the Great Dragon's breath. Arthur was to fight de Bois but Uther took Arthur's place and used the sword to defeat Tristan de bois. (Excalibur)

Later in the series, Tom is working for Tauren, who uses magic to create gold Tauren pays him so he can buy things for Gwen. Unknown to Tom that Tauren is a sorcerer. Tauren then decided to finally turn lead into gold using the mage stone. The lead turns into gold and Tom amazed at what he see's pick up the gold. Tauren said he could have it. But they were interupted by Arthur and the guards. They arrest Tom while Tauren escapes and Uther condemns Tom to death believing, Tom is forging weapons for Tauren. They have a discussion Morgana objects to Uther excecuting Tom and says she will never forgive him if he does. Arthur also objects. But Uther says he'll get a trial and he'll be found guilty because that's what he is. Gwen visits Tom in his cell To get information about the situation to tell Merlin and Gaius. She tells him that she promises to get him out before she leave's.

Morgana, realising Tom's trial is merely a formality, gave Tom the key to escape. But his disappearence was reported and Uther makes the trial a formality and orders that if Tom is seen he will be killed on spot. Tom was eventually caught and surrounded by guards and killed on the spot, leaving Gwen an orphan. His corpse is being  out by two soldiers and bathed in Gwen's tears. His death also drove Morgana to conspire with Tauren to murder Uther however this assasination plan led to Tauren's death. (To Kill the King)

Personality
According to Merlin, Tom was the most gentle soul he'd ever met. As he has only appeared in two episodes, full knowledge of his personality is unknown, but he loved his daughter Guinevere and was determined to make her happy. Unfortunately his determination to make a better life for him and Gwen cost him his life when he was discovered working for Tauren even though he hadn't intended to commit treason.

Ablities
According to Gaius, Tom was the finest blacksmith in the kingdom. He forged the sword that would become Excalibur after it was imbued with the breath of Great Dragon.

Appearances
Series 1:

The Mark of Nimueh (first appearance)

Excalibur (mentioned only)

To Kill the King (dies)

Series 2:

The Witchfinder (mentioned only)

Series 3:

The Castle of Fyrien (mentioned only)

Queen of Hearts (mentioned only)

The Coming of Arthur: Part Two (mentioned only)

Series 4:

His Father's Son (mentioned only)