"Card storyline" is an unofficial term for the stories that can be pieced together regarding the relationships between certain monsters and groups of monsters from card artworks.
Many of these stories were detailed in the Japanese Master Guide books.
"Dark Ruler Ha Des"
Dark King of the Abyss was a very powerful ruler of darkness. Dark Ruler Ha Des first appeared when he dethroned Dark King of the Abyss and took control of everything evil. He was a merciless tyrant who built an entire army of shadow creatures. He had his minions trust him mentally, but wasn't above on using his minions to protect him from any attacks directed at him. "Opticlops" and "Berserk Dragon" were two of many creatures that he valued the most. He was often seen having dealings with shady people or acting as the judge for criminals. Besides his army, he was extremely powerful by himself, being able to control free, weaken his enemies with his roar, and destroy them in many ways. However, he eventually lost control of his powers.
One day he was confronted by his rival, who, after gathering his hatred for so long had struck back using this hatred as his power against his dethroner. After Ha Des was more than weakened enough, Dark King of the Abyss casted a curse upon Dark Ruler Ha Des, using a severed head to drain his soul. Afterwards, Dark King of the Abyss transferred the soul into himself to augment his power.
The result of the battle was fatal for the Ha Des. However, that wasn't meant to be the end, since he was later revived, by the very same plague that had changed many other monsters into zombies, including Archfiend Zombie-Skull and Doomkaiser Dragon. Later, he faced his nemesis and ultimately defeated him, thus ruling over darkness once again.
Unfortunately, his rival was revived as well, becoming even more powerful than before, which Ha Des and his army witnesses.
"D.D. Warrior Lady"
Originally a wandering outlaw, for some unknown reason she and Warrior Dai Grepher became rivals. During their fight, she was abducted to the Different Dimension. There she found comrades which helped her train herself in traveling between dimensions. Then, using the Different Dimension Gate, she was able to return from the Different Dimension along with some other creatures who were lost there.
Upon her return, she engaged her rival in another fight, where she used her new powers to injure him, apparently beating him. Later, her rival returned for revenge in a darker form, but she banished him to the Different Dimension again. At some point prior to meeting Warrior Dai Grepher, she was allied with the Marauding Captain, using a Resonance Device to make their levels the same.
Gagagigo spent his younger days serving Eria the Water Charmer as her familiar. During this time, he fought alongside her and many others. While in his younger days, he was nearly eaten by some monster plants while trying to get food, but was presumingly saved by Eria. He grew up into Jigabyte and then to Gagagigo. He continued to serve as Eria's familiar for a long time until he and the Familiars of the other Charmers unleashed their full potential.
After that, Gagagigo went on to follow his own path of evil. He saw food that was being made for Freed the Brave Wanderer and tried to take the food, but got into a scuffle with Freed the Brave Wanderer. They both started to fight and somehow Gagagigo got dragged into the other dimension through the Dimensional Prison.
Bent on revenge, he started a journey to find a way back to his dimension and arrived on what seems to be a cemetery. He joined Invader of Darkness and his group of demons, only to be betrayed later on by Invader of Darkness himself. He ended up fighting in a cell battle, along with Marauding Captain and Blazing Inpachi. Thanks to Marauding Captain, he was saved from a blast launched by Blazing Inpachi and turned good to help his newfound friend.
At some point later, Gagagigo fought the Goblin Attack Force (who were enemies to the Marauding Captain) in an icy area, but their attack failed due to their inability to ice skate and Gagagigo's mastery over ice skating. He would then join Marauding Captain in a war against Invader of Darkness, and protect one of Marauding Captain's men from Invader of Darkness. However, after being hit by a blast, Gagagigo was severely injured and in need of immediate support.
He went on to gain aid from Kozaky, who was a spy among the warriors, and got his body reconstructed, turning him into Giga Gagagigo. However, Giga Gagagigo was turned against his friends by Kozaky's Dark World technology. Giga Gagagigo was sent back to his dimension thanks to a machine, which opened the Monster Gate. He became a fighting machine and sought more power. He first fought Venom Cobra to test his strength. After seeing how powerful he had become, he decided to find a new opponent. He then soon battled and attacked Freed the Brave Wanderer again, but failed. Due to his cybernetic implants, he became power-hungry and transformed into Gogiga Gagagigo. Gagagigo had been driven mad by cybernetic enhancements given to him by Kozaky.
After attaining his new form, Gogiga Gagagigo" at some point fought Inpachi again and defeated him. After his victory, he took the head of Inpachi as a trophy. He later fought Invader of Darkness again and presumingly defeated him. After taking Invader's body with him, Gogiga Gagagigo soon fought Freed the Matchless General again for revenge, but was stopped by his savior, Marauding Captain, who reminded him of what he once was before being mechanized. This purifies Gagagigo and transforms him into Gagagigo the Risen.
Gagagigo the Risen would later fight an unknown opponent. The opponent threw many green energy shards at him, but Gagagigo used a red coat he obtained to protect himself. Later, Gagagigo fought Sword Breaker. During this fight, Sword Breaker captured Gagagigo and stole one of Gagagigo's Xyz Materials.
"Goblin of Greed"
Goblin of Greed was a wealthy dealer with many goblin minions under his command before he lost his money in an accident. With nothing left, Goblin of Greed attempts to get wealthy like he once was. He first tried earning money by becoming a beggar and using a Pot of Duality, however he found that the method was too slow for him to become wealthy. He then tried working in housekeeping service, but almost lost everything. He was fired and started to steal Jar of Greed and then Pot of Greed. Later Goblin of Greed angered an important aristocrat, presumably by either being caught stealing the pot or offering him the stolen Pot of Greed. Goblin of Greed was then placed into slavery.
The Dark Scorpion Burglars later tried stealing the wealthy man's money and Pot of Greed and somehow succeeded a bit. Goblin of Greed was on their tail but was interrupted. Goblin of Greed was able to retrieve the pot, but the "Spirit of the Pot of Greed" was somehow released and started creating a twister that was absorbing cards into it and subsequently curse Goblin of Greed. Dharc the Dark Charmer appeared and then somehow resealed or captured the spirit to prevent it from doing any further harm and return "Goblin of Greed" to normal, but the Pot of Greed got broken in the process. Goblin of Greed was later fired when the aristocrat found the broken Pot of Greed and Goblin of Greed couldn't pay for it.
While trying to find a new way to get wealthy, Goblin of Greed tried looking for a part-time job, one of which was mowing the lawn on a wealthy estate. However he failed because of pollen allergy. Goblin of Greed later lost all of his money by paying for the stolen and damaged Jar of Greed and Pot of Greed. Despite paying all of his money for the stolen and damaged items, the store owner didn't accept the money and threw it back at Goblin, considering the money worthless. He then threw Goblin of Greed out of the store and got him temporarily arrested and imprisoned for stealing and damaging the merchandise.
After Goblin of Greed was released, he would, at a later point, come into a bazaar in a desert where he tried to perform using the broken Pot of Greed and a Sinister Serpent. However the Sinister Serpent he uses for the performance attacks him, which ruined the performance. Later he would trade the slightly broken Pot of Greed for a Pot of Duality. The goblin that Goblin of Greed made a trade with would then give him payment in return.
Rumors say he's currently working in an abandoned dark factory. In the factory were two more Pots of Greed and he tried to steal them. He succeeded in this and later sold off the Pots for extra money.
Originally a big tree in the forest, Inpachi was cut down and possessed by a wicked spirit. It then became evil and started to attack many people that entered its lair, including an armored man that cut him into three pieces.
Later, he was revived by unknown means, and abandoned his home to seek revenge on his newly acquired archrival. While searching for his nemesis, he fought against a criminal. He was nearly defeated, but his angered soul flared up as he wouldn't accept defeat. With his new form, he encountered his rival once again and the two started to battle. However, a strange lizardman appeared and helped the armored man to defeat Blazing Inpachi, leaving it in a burned-out state upon its defeat.
Inpachi rejuvenated back up at some point and later fought the lizardman again, but with the latter now with cybernetic implants and a dying thirst for power. The lizardman defeated Inpachi and took its head away as a trophy.
Later a mysterious scientist Kozaky came upon Inpachi's body. Out of intrigue, he decided to reconstruct its corpse into a cybernetic form, with the help of cutting-edge Dark World technology, including giving it a new head. At some point later, Woodborg Inpachi battled Kick Man, but lost and was subsequently destroyed.
"Legendary Six Samurai"
Petit Dragon began his journey becoming the familiar of Wynn, gaining more power as they both grew stronger. One day he decided he wanted to be able to breath fire, so he sought out a plant to give him this power. However, once he ate the plant his body ignited, and he was turned into a vicious dragon.
Bent on becoming a more threatening force, he combined powers with four other dragons, making them all become nearly invincible, until the day when they were defeated by a powerful foe. The knight sealed Darkfire Dragon's soul inside a sword. This sword was then wielded by the Flame Swordsman.
Sangan is going on a tour to the living world on the Tour Bus From the Underworld. However, at a platform, it mistakes the Tour Bus To Forbidden Realms (driven by the first fiend from Delinquent Duo) with Tour Bus from the Underworld (while Tardy Orc missed the bus). On the bus trip, the Graceful Charity angel tries to comfort Sangan. Later, the passengers are arrested for carrying a "Pot of Greed". Sangan and Witch of the Black Forest were placed into the same cell, where Sangan begs to the security guards to release him.
"Skull Servant" and other "Wight" monsters
Tales of the Noble Knights
The Tales of the Noble Knights has card storylines regarding some of the "Noble Knight" monsters and their various support cards.
"Warrior Dai Grepher"
Born poor, Warrior Dai Grepher grew up with little else except confidence in his sword thanks to his battles with many monsters, most notably Vennominaga the Deity of Poisonous Snakes. Trying to find his way in the world, he was confronted on the field of battle by a mysterious woman who soon became his greatest rival. Their first battle ended when a mysterious force disarmed them both; their next battle concluded with her being abducted into an other dimension, from which she returned even more skilled than before. Then he found allies and they eventually fought together in a war against and many demons. Although he is saved by his team's Spellcaster from a demon attack, Dai Grepher is transported into another dimension.
There, he finds himself at The Paths of Destiny. Picking the path of light, he befriends a strange dragon, who grants Dai Grepher his power. He later acquired a new sword and became a heroic knight. He then found two powerful swords of light which worked with him. He would later enter a time portal universe where he made contact with his alternate future dark self.
In an alternate timeline, Dai Grepher would take the dark path instead of the light path. He later discovered he was fighting an evil version of himself who would remain his adversary for a while. He later fought Umbral Horror Unform, but found himself outmatched by the creature. His adversary appears again and they worked together to defeat the dark beast. The adversary sacrifices his power to Dai Grepher in order for Dai Grepher to destroy the Umbral Horror Unform, but while the beast was defeated, Dai Grepher's weapon was damaged and rendered useless.
After defeating another great demon through unknown means, Dai Grepher takes up the demon's sword to replace his broken sword. Unfortunately, the demon that Dai Grepher defeated was but an extension of its sword and eventually sought Dai Grepher's body. Eventually, he submitted, becoming a rampaging monster. Later he fought his rival again and was sent back to the different dimension. Going through the dimension hole, Dai Grepher ends up in a time portal universe where he made contact with his light future self. Both were surprised at seeing each other, but in response to Dai Grepher seeing a righteous version of himself, the darkness in Dai Grepher corrupted him even more, until, at the height of his mutation, he was completely unrecognizable as his former self.
Gagaga Academy Tospedia
The Gagaga Academy Tospedia has card storylines for the Fire Kings, the Atlantean's invasion of the Mermails, the Gishki's invasion of the Gusto, The Dragon Rulers, the Bujins, the Spellbooks and Prophecy, and the Ghostricks.