CodeMaster Crellan is the CodeMaster of the Crellan drome. His appearance is that of a young adult male. His first appearance was in the episode "Battle Lessons," where he appeared in his normal human form and in his Code Master suit. In Battle Lessons, Tom discovered Code Master Crellan (human form) hanging and losing his grip from a cliff in RockRiver Canyon. At that time, however, Tom didn't realize that the player he'd rescued was a Code Master. Afterwards, Crellan offered to give Tom a few tips on how to be a good player without his Maxxor card. Both later met again at the Beta Drome, where Tom unsuccessfully tried to defeat Crellan's single creature, Ursis, as five of his creatures were defeated by Crellan as Ursis. Then before the last battle of the match, Tom came to the realization that Crellan was actually a Code Master, just before Crellan transformed into his Code Master outfit. The two then fought the last battle of the match, in which Tom, as Tangath Toborn, managed to nearly defeat Ursis. However, Crellan managed to use Song of Translocation Mugic to change the location, and finished Tangath Toborn. Afterwards, Crellan had disappeared when Tom rematerialized in the drome.
Tom later re-battles CodeMaster Crellan after winning 7 battles in the Crellan Drome and manages to win thanks to the Mugic that Klay and Krystella had tricked him into scanning, much to their discontent. Tom thought he was scanning a Mugic called Modulation which was supposed to double his energy but it actually switches the disciplines (elemental capabilities) of the player's creature with that of the opponent's creature. During the match Tom ends up fighting against one of Crellan's strongest creatures, Cromaxx, a savage version of Maxxor. He wins by defeating Crellan's creature Ariak (which had the ability to bring back other creatures) and then used Maxxor to battle Cromaxx at Kiru City. Tom's strategy was then to run into Maxxor's castle in order to gain a Mugician, which would allow him to cast a Mugic. He casts his new Modulation Mugic and it allows him to switch abilities with Cromax. When Crellan is defeated, he rewards Tom with a Prexxor Chasm scan.
Smildon later makes a reference to him when Tom visits Prexxor Chasm.
Codemaster Crellan was with Imthor when he arrived at the scene of the conflict where Dimitri and his followers were going to detonate a location with explosive BattleGear stolen from Kiru City's weaponry.
Kaz mentions to Tom that he fought CodeMaster Amzen once and lost as Chaor when Amzen used a Battle Gear that turned him into a shock absorber.
The CodeMaster of the Tirasis Drome. Battle Drome Tirasis was first referred to in passing when Kaz was saving Drew from all the players that wanted challenge him in the episode "Allmegeddon." In the episode "Dual, Duel Part 2", Sarah had a match in Battle Drome Tirasis.
CodeMaster Imthor makes a brief battle appearance against Klay during The Codemaster Chronicles in which Tom re-battles Code Master Crellan. Imthor beats Klay with a large, invisible creature (possibly a Mipedian Warbeast). Considering the size and shape of his invisible creature's footsteps, he may have been using a Mipedian with Fortissimo Mugic or one of the Warbeasts.
In "Fighting Friendly", Tom and Kaz later faced off in the Imthor Drome to determine who will face off against Code Master Imthor. After a battle where Tom as Najarin faced off against Kaz as Lord Van Bloot, Kaz accuses Tom of cheating afterwards, claiming that Tom somehow knew what cards he would use. He reasoned that neither Tom nor any other player would ever have equipped Najarin with a Torwegg Battle Gear unless he either had a Hymn of the Elements mugic or knew for a fact that Kaz would use his Stronghold Morn location. Imthor was sent down to look into this. After discovering Tom lied about having a Hymn of the Elements card in his deck, Imthor states that he will discuss this matter with the other Code Masters. This results in Tom being banned from Chaotic matches till further notice.
It is later revealed in the following episode that Tom and Kaz put on that ruze when they learned from Maxxor that some Chaotic players have been stealing explosive BattleGear and using them to detonate rare locations. Kaz and Tom came to the Codemasters and later on in the episode's climax, Imthor and Crellan arrived and stopped Dimitri and his followers from leaving the scene of the conflict by deactivating their Scanners.
Sarah mentioned to Tom that she fought CodeMaster Chirrul once and lost as Junda when Chirrul trapped her in a bubble and spun her at high speeds. Sarah claims that she's still dizzy from that battle.