Its appearance, Graveyard-centric effect and relationship to Seto make it loosely reminiscent of the card "Swordstalker", which was used by Seto Kaiba.
When the High Priests partook in mock battles to strengthen their ka and improve tactics, Seto summoned Duos. Initially its teammates and their opponents used various abilities to counter each other's moves. Once its teammates, Dark Ushebti and Zerua had outlived their usefulness, Seto got Duos to destroy them, since its power increased through sacrifice. With its strength tripled, Duos took out its enemies Magus of Illusion, Spiria and Desert Trapdoor Spider in one blow.
Duos was summoned again for Atem's demonstration of the pitfalls of Seto's reckless strength-driven battle strategy. Seto was insulted by Atem's choice of a weak ka, Kuriboh, and got Duos to try and destroy its slab, before the ka could materialize. However a Kuriboh emerged from each fragment of the shattered slab and covered Duos' arm, making it unable to use its sword.