Cletienne has slicked back dark brown hair (light brown in the mobile app version) with two short fringes on each side and black eyes. Like most templar knights, despite his job as a sorcerer, he wears golden armor with a long gray/silver hooded cloak, golden pants with a gold belt at the side of his cloak, and golden boots.
In the mobile app version, his cloak changes into a different shades of gray and his belt is light brown, and his pants are now bronze and his boots are now brown.
Before he follows the fellow knight templar, Folmarv Tengille and Loffrey Wodring, to Mullonde Cathedral, Cletienne meets Ramza Beoulve in Merchant City of Dorter. Ramza is on his way to Eagrose Castle to stop his elder brother, Dycedarg Beoulve, who has been given the Capricorn Auracite by Loffrey, which Ramza knows puts him in danger of being possessed by a Lucavi demon.
Cletienne traps Ramza by binding him with magick, stating it is of his own craft. As he attempts to finish Ramza off, Meliadoul Tengille, Folmarv's daughter, attacks him from behind and Cletienne recognizes her. Meliadoul explains that she and her younger brother, Isilud Tengille, have been used by the templars and the Church of Glabados. Cletienne is defeated by Ramza and Meliadoul, but before he teleports away Meliadoul asks if her father is possessed by a Lucavi. Cletienne tells her to go see for herself.
Cletienne accompanies Folmarv and Loffrey in Mullonde Cathedral to betray the High Confessor Marcel Funebris, as the three deem they no longer need the church's allegiance. The templars force Funebris to divulge the location of the portal to the Necrohol of Mullonde before Loffrey mortally wounds him. On their way out, they are confronted by Ramza and Meliadoul, who tries to ask her father if he is possessed and killed her younger brother, Isilud. Folmarv confirms, and after gaining the Scriptures of Germonique from Ramza, they flee by teleportation.
They journey to Orbonne Monastery where the portal is located as per the scriptures. After posting a contingent of knights on the fourth basement of the Underground Book Storage, the three descend to the fifth level where Loffrey opens the portal, allowing Cletienne and Folmarv to cross over to Mullonde. Knowing that Ramza would likely pursue, Folmarv orders Cletienne to remain behind to guard the entrance before continuing alone to the Airship Graveyard.
Cletienne is fought three times (twice originally in the PlayStation version); the first battle being at Mullonde Cathedral Nave, the final battle at Necrohol of Mullonde, and the other in an optional battle at Merchant City of Dorter. In the optional battle, he is level 40 with 51 Bravery and 81 Faith, and comes equipped with the rare Dragon Rod, as well as a Gold Hairpin, Elven Cloak, and Gaia Gear.
He has access to powerful spells via his Magicks command, and also uses the Magick Counter, Arcane Defense, and Ignore Elevation abilities. In this battle, he is immune to all negative statuses except Blind, Silence, Oil, Slow, and Immobilize.
It is not required to defeat all enemies or KO Cletienne; simply reducing his HP to 20% of his max HP is enough to win the battle. This battle will disappear if not done before completing Eagrose Castle. In the first actual battle at Mullonde Cathedral, he is level 45 but retains everything from the exclusive optional battle in War of the Lions.
In the final battle at Necrohol, he is level 54 and equipped with the Zeus Mace, Lambent Hat, Black Garb, and Featherweave Cloak. He has access to Magicks, Magick Boost, Arcane Defense, and Fly, and is immune to all negative statuses except the ones from previously. Clientienne is the only character can cast Dark Holy magick during his third and final fight with Ramza.
Cletienne can be fought in the War of the Lions remake, in the tenth Rendezvous battle: The Knights Templar. Here, he is 5 levels higher than the highest leveled deployed unit, and has 51 Bravery and 81 Faith. He comes equipped with a Wizard Rod and other random equipment, and has access to Magicks while his other abilities are randomized. He is immune to the same statuses as previously.
When fought in the fourteenth Rendezvous battle: Brave Story, he is level 99 and starts with 97 Bravery and 81 Faith. He comes equipped with Wizard Rod, Thief's Hat, Luminous Robe, and a random accessory. He has access to the Magicks command, as well as to the abilities Magick Counter, Arcane Strength, Manafont, and another random ability. He is immune to the same statuses as previously.
Cletienne was named after Chrétien de Troyes (クレティアン・ド・トロワ, Kuretian do Torowa?), a medieval French writer of heroic poems and novels.