To pass the stage, Dark Yugi had to answer the riddle "What creeps on the ground and clings to the pillars?", while being handled by zombies.
Shadi created the illusion that zombies were coming out the ground and grabbing onto Dark Yugi. The corpses were just an illusion and Dark Yugi needed to find their true nature to pass the stage. Shadi gave him the riddle, "What creeps on the ground and clings to the pillars?" as a hint to find out what the illusion really was.
Although Dark Yugi knew that the corpses were an illusion, he couldn't break free from it. He tried to relax and find the answer the riddle, hoping that would make the illusion go away. He figured that the corpses were what creeps on the ground and he was the pillar. He tried looking at it the other way around, thinking of a pillar and wondering what comes off of it onto the ground. He realized that the answer was a Shadow and that the illusion's true nature was his own shadow. Once he announced this the illusion disappeared.
- Yu-Gi-Oh! Duel 17: "Game Start!"