The ventriloquist used the puppet while Kaiba was in a coma after Dark Yugi inflicted the "Mind Crush" Penalty Game on him. The ventriloquist used the puppet during his Duel with Dark Yugi. He spoke through the puppet, which he claimed to be the real Seto Kaiba borrowing the body of the puppet to get revenge on Dark Yugi. He also got the puppet to play his cards. He had the puppet speak with a stutter and a sadistic attitude. All this made Yugi fear that Kaiba forsake redemption and faith for revenge. The purpose of the puppet was meant to make Yugi lose his concentration and confidence.
When the real Seto Kaiba woke from his coma, a "Blue-Eyes White Dragon" played by the ventriloquist destroyed itself. This caused the ventriloquist to drop the puppet in surprise. From that point on, he continued the Duel without using the puppet.
After Dark Yugi won the Duel, he inflicted a Penalty Game on the ventriloquist, where the ventriloquist believed the Kaiba puppet transformed into a living puppet of himself and began to torment him.