Series 1

Series 1 of Merlin ran between 20 September and 13 December of 2008. The series introduced the protagonist Merlin, as well as his master and eventual friend Arthur Pendragon, and his tutor Gaius. The primary antagonist of the series is Nimueh, a powerful sorceress exiled by Uther Pendragon when Arthur was born.

The arch focuses around the destinies of Merlin and Arthur, and those who wish to prevent them. It also focused on the question of life and death. The series chiefly involves Merlin coming to terms with his powers and using them to protect Arthur as well as other characters. The series consisted of thirteen episodes, each with a running time of roughly 45 minutes.

Specials
Children in Need
 * Merlin in Need (2008) – 14 November 2008

Main cast

 * Colin Morgan as Merlin
 * Bradley James as Prince Arthur
 * Richard Wilson as Gaius
 * Anthony Head as Uther Pendragon
 * Angel Coulby as Gwen
 * Katie McGrath as Morgana
 * John Hurt as The Great Dragon

Recurring cast

 * Michelle Ryan as Nimueh
 * Michael Cronin as Geoffrey of Monmouth
 * Caroline Faber as Hunith
 * David Durham as Tom the Blacksmith

Guest stars

 * Eve Myles as Mary Collins/Lady Helen (The Dragon's Call)
 * Will Mellor as Knight Valiant (Valiant)
 * Clive Russell as Bayard (The Poisoned Chalice)
 * Santiago Cabrera as Lancelot (Lancelot)
 * Julian Rhind-Tutt as Edwin Muirden (A Remedy to Cure All Ills)
 * Kenneth Cranham as Aulfric of Tír-Mòr (The Gates of Avalon)
 * Holliday Grainger as Sophia of Tír-Mòr (The Gates of Avalon)
 * Asa Butterfield as Mordred (The Beginning of the End)
 * Kyle Redmond-Jones as Sir Owain (Excalibur)
 * Sean Francis as Sir Pellinore (Excalibur)
 * Rick English/Christopher Fairbank as Tristan de Bois (Excalibur)
 * Alexander Siddig as Kanen (The Moment of Truth)
 * Joe Dempsie as William (The Moment of Truth)
 * Frank Finlay as Anhora (The Labyrinth of Gedref)
 * Cal MacAninch as Tauren (To Kill the King)

Cast Notes
Michelle Ryan who played Nimueh featured in four episodes who was originally supposed to only appear in three episodes but was asked to do more because the producers were so impressed with her performance.

Enemies and creatures

 * The Great Dragon
 * Mary Collins
 * Knight Valiant
 * Afanc
 * Cockatrice
 * Giant spiders
 * Griffin
 * Edwin Muirden
 * Aulfric of Tír-Mòr
 * Sophia of Tír-Mòr
 * Sídhe
 * Mordred
 * Tristan De Bois
 * Wraith
 * Kanen
 * Anhora
 * Unicorn
 * Tauren
 * Questing Beast
 * Nimueh