Guardian of the Labyrinth, known as Guardian of the Underworld in the Japanese version, is a character version of the card "Guardian of the Labyrinth", who appears as part of The Supreme King's army in the alternate dimension in Yu-Gi-Oh! GX.
The Guardian's shield does most of the talking, with the Guardian himself only responding to what the shield says by saying "exactly" (in the dub, the Guardian uses different words when responding).
Guardian of the Labrinyth appeared alongside Skull Knight while the latter was disguised as "Ancient Brain". The two infiltrated the final free town in the alternate dimension. Skull Knight planned to report back to the Supreme King, telling the Guardian to throw open the gates of the village when the King's forces arrived. Axel Brodie confronted them and Skull Knight revealed his true form, challenging Axel to a Duel.
When Skull Knight was defeated, Axel captured both the Guardian and his shield. What happened to the Guardian himself after this is unclear, but Axel took the shield hostage to use a guide while infiltrating The Supreme King's castle. He, Zane Truesdale, and Aster Phoenix disguised themselves in the armor of "Dark Blade" and infiltrated the castle. They were confronted by Chaos Sorcerer, who questioned what they are doing. The shield responded that they had a message for the Supreme King from Skull Knight. Chaos Sorcerer pretended to let them go, but then attacked, revealing that all messages from Skull Knight were to go through him prior to reaching the King. The shield revealed their true identities, telling Chaos Sorcerer that the three were here to confront the Supreme King. Despite this, Chaos Sorcerer killed the shield for its treachery.
- Yu-Gi-Oh! GX episode 141: ""
- Yu-Gi-Oh! GX episode 142: ""