He was voiced by Steven Jay Blum (Guilmon) and Brian Beacock (Takato) together.
He resembles an exalted knight that is clad in holy white armor with a long red cape and it's right hand can become a jousting spear and the other hand carries a holy shield.
He is a dragon-like knight warrior. He wields a lance and a shield just like other knights in fairy tales.
Gallantmon is the true Mega form of Guilmon. Gallantmon was the first Biomerged Digimon to appear. Gallantmon first appeared when Takato Biomerged with Guilmon in order to fight Beelzemon. In this new form, Gallantmon was able to defeat Beelzemon. He also destroyed Caturamon during the battle, but it was Beelzemon who absorbed his data. Gallantmon's power proved a major asset in the battle against the D-Reaper. Gallantmon played a key role in confronting the D-Reaper and in obtaining the ARMS "Grani" as his mode of transportation.
In the English version he often speaks with a merged voice between Guilmon and Takato, representing that he is a fused dual entity of the two both physically and mentally and often retains the childish mentality of Guilmon in part. Whereas in the Japanese, he speaks with a single voice (Takato can speak separately, though) and is much more 'mature' in mindset, speaks in a refined manner, often referring to himself by saying "I, Dukemon" and Takato even refers to him internally as Dukemon (however he does refer to him internally as Guilmon just before they split apart from being Gallantmon Crimson Mode). He can even be hotblooded in battle, particularly when he defeats Beelzemon.
Gallantmon Crimson Mode is the mode form of Gallantmon. Gallantmon Crimson Mode appeared towards the end of Digimon Tamers. Gallantmon had found himself overwhelmed in his battle against the D-Reaper. In his time of need, Grani gave the last of his power to Gallantmon triggering a mode change. In his newly digivolved form, Gallantmon gained wings and newly mended crimson armor, wielding a sword “Blutgang” in one hand and spear “Gungnir” in the other. While in mode form, the Digital Hazard within Gallantmon's Digicore is fully sealed, enabling Gallantmon to unveil his full potential. With this newfound power, Gallantmon Crimson Mode was unable to defeat the D-Reaper's Agent-01. Agent-01 destroys his weapons after he easily destroys many other agents and knocks him into the Mother Reaper causing him to start to delete. Gallantmon Crimson Mode pulls himself together, flies out and punches his fist through Agent-01 destroying it. He goes on to attempt to rescue Jeri and Calumon but due to an error in the Red Card's effects due to Shibumi not taking into account the Digimon/Human hybrid he de-digivolves back into Takato and Guilmon before he can succeed.
During the final battle with the Parasimon, Gallantmon and his allies are outnumbered and being overwhelmed. Takato's determination to win causes Gallantmon to tap into the power that Grani gave him and Mode Change into Crimson Mode. Gallantmon Crimson Mode is able to easily destroy all the Parasimon in one shot with his Crimson Light attack ending the invasion and saving the Earth. This is Guilmon's most powerful form and likely the most powerful Digimon in Digimon Tamers, (probably) excluding the Digimon Sovereigns.
Gallantmon is a member of the Royal Knights who questioned the intentions of the host computer, Yggdrasill. Because of this, Gallantmon acted individually, and tried to convince his close friend Omnimon that they were just being used and that their master Yggdrasill's Project Ark was more than it seemed. However, Omnimon refused to listen, and killed Gallantmon in a duel and is revealed that Gallantmon wanted to be deleted so that he may further invesitage Yggdrasill's intentions. Gallantmon was soon reborn as Gallantmon X, with the X-Antibody.
Gallantmon X appeared to help Dorugreymon, WarGreymon X, MetalGarurumon X, and the others fight off the great numbers of DexDoruGreymon and ordered the others to lead them out of the hidden road, and that DoruGreymon will stay and help him fight off the remaining enemies. DoruGreymon asked him why he existed and if he was dead, none of the dangers would have happened.
Gallantmon X asked him if he wanted to know the reason he existed and opened the gate to Yggdrasill's lair. After Omnimon X destroyed Yggdrasill, which caused the Digital World to reset, Gallantmon X is seen surveying the landscape along with Omnimon X. Then Gallantmon X said to Omnimon X that he was beginning to understand the reason behind Project Ark. Gallantmon X said that Yggdrasill generally intervened in the Digital World, but the world is a complex place, and that is where it thought about 'fixing it'.Omnimon X asked him if that was really Project Ark, and Gallantmon X told Omnimon that it was the most likely reason behind it. Gallantmon X said that was the time it thought up the experimental being, Dorumon,and they were merely just pawns of Yggdrasill's plan and Yggdrasill merely wanted to live, and said that from now on, all the digimon can be happy.
- He is an Exalted Knight Digimon whose Japanese name is derived from "Duke", and whose English name is derived from "Gallant". One of the "Royal Knights", it is a being containing contradictions, as it is of the Virus attribute while also being called a guardian deity of the Net.
- If its stability collapses, even due to a freak chance, it is possible for it to become a dangerous existence. It pilots the Flying Dragon machine "Grani", as a dragon knight that races across the skies. It is clad in holy armor refined and constructed from 99.9% pure Chrome Digizoid, and its right hand can become the holy lance "Gram" while its left hand can become the holy shield "Aegis".
- It honors chivalry, and is a loyal vassal towards its lord. Its cuirass and poleyns are adorned with the symbol of the Digital Hazard, its forehead and Aegis bear the Zero Unit, and the DigiCode on its Aegis reads Digital Monster.