Its effect name is "Nightmare Pain" in the original.
In episode 155, Yubel uses this card during her Duel with Jaden. She Special Summons this card via the final effect of "Yubel - Terror Incarnate". On Yubel's next turn, this card attacks "Rainbow Neos", but Jaden activates "Alchemy Cycle" to reduce the ATK of "Rainbow Neos" to 0 and prevent it from being destroyed by battle. Since this card can't be destroyed by battle, the attack ends in a stalemate. After damage calculation, the final effect of "Alchemy Cycle" banishes "Rainbow Neos" and allows Jaden to draw a card. Later this card attacks "Elemental HERO Neos", but Jaden activates "Mirage Tube" to negate the attack and inflict damage to Yubel equal to the ATK of "Neos". The second effect of "Spell Chronicle" then activates, giving it a second Chronicle Counter. Yubel then activates the third effect of "Spell Chronicle" to make Jaden choose one of the two remaining cards banished by "Spell Chronicle". Jaden chooses "Super Polymerization", so the latter is added to Yubel's hand. Yubel then activates "Chain Material" to let her banish monsters in her field, hand, Deck, and Graveyard and use those monsters as Fusion Material Monsters when she performs a Fusion Summon this turn. After choosing twelve monsters (which were "Grave Squirmer", "Giant Germ", "Chaos Core", "Phantom of Chaos", "Dark Summoning Beast", "Infernal Incinerator", "Maju Garzett", "Lava Golem", "Infernal Flame Emperor", "Raviel, Lord of Phantasms", "Gate Guardian", and this card) each with a consecutive Level from 1 to 12, Yubel activates this card to banish her twelve selected monsters from her Deck and field in order to Fusion Summon "Super Fusion God" (whose Summoning would unite the twelve dimensions into one), but Jaden activates "Spiritual Fusion" and selects to use "Super Polymerization" to fuse his soul with Yubel's. By doing this, Jaden frees Yubel from the Light's influence and unites her with the Supreme King forever.
In episode 158, this card is shown in series of flashbacks Sartorius has when he explains that while the earthquake-like energy that is about to erupt on the island is nothing more than a hypothesis, the incidents involving the Sacred Beasts, the Light of Destruction, and Yubel have caused a lot of pressure to the dimension centering the Duel Academy island, which will cause another bad affair to happen.
In episode 178, this card is shown in a series of flashbacks Jaden has when he tells the people trapped in the World of Darkness that the card that a Duelist bonds with is initially just a plain card without anything special, however people that a Duelist fight against and the feelings that were shared among those people as well as the memories of those Duels will be absorbed into the bonded card as it's the history of a person's efforts.
The flashback Jaden saw when Yubel was human implies that this is Yubel's true form, since the man, the king of a country when they lived, who Yubel (when she was human) was talking to, described the form that Yubel would take to protect Jaden as a "hideous dragon" in the Japanese version.
Yubel was shown to have merged with this form, like her previous incarnation. In this case, it burst through the forward-facing horn on "The Ultimate Nightmare's" devil head, eliminating it and replacing the face with Yubel's body from the torso up.
In the Japanese version, the card is shown on Yubel's Duel Disk facing her. In the dub, it was moved to be facing the opposite way, but was incorrectly shown to be a WIND monster. It also appeared with its correct attribute in the "Chain Material" sequence in the dub, in the place "Gate Guardian" occupied in the original.