"A Snake in the Grass, Part 1", known as "Decisive Battle! Judai VS Professor Cobra" in the Japanese version, is the one hundred and seventeenth episode of the Yu-Gi-Oh! GX anime. It first aired in Japan on January 3, 2007 and in the US on September 1, 2007.
Axel finally manages to escape from Viper's trap. With both Mr. Stein and Trapper defeated, Jaden and Jesse are both exhausted. Both argue slightly about which direction to go. Jesse wants to go forwards a take on Viper; whereas Jaden, concerned about his overconfident friend, wants to go back and find the others. In the end they agree to stay put and wait for the others to come. Eventually Jaden and company converge to finally confront Viper. While doing so, Adrian meets up with Viper in order to take a particular card for the Gecko Family and they engage in a fist fight. Although he leads, Adrian is paralyzed by the demon in the tank. After passing several traps with Axel's help, Jaden and the others finally meet Viper. While Axel stays beind and his fate is unknown, Viper and Jaden engage in a Duel. Although starting out enthusiastically, Jaden is quickly driven back by the weakening effects of Viper's Venom Deck.
Adrian is still trapped in the room where he met Viper, and the Duel Monster Spirit in the tank begins to attempt to convert him to it' side. It brings back memories of his childhood. After he was adopted by the Gecko Family, he trained himself both physically and mentally to be a worthy heir. However, once the Geckos had their own biological son, Shido, he began to be ignored by his parents. Only Echo still remained by his side.
Viper then sets two cards and activates "Venom Swamp". Now all monsters on the field will lose 500 ATK for each Venom Counter that they have on them ("Clayman": 800 → 300/2000). If a monster's ATK is reduced to 0 by this effect, that monster will be destroyed. During each player's End Phase all face-up non "Venom" monsters will have a Venom Conuter" placed on them.
On Viper's End Phase, "Venom Swamp" places a Venom Counter on "Clayman" ("Clayman": 300 → 0/2000). The third effect of "Venom Swamp" then activates, destroying "Clayman".