Trishula is a minor antagonist in the lore of the "Yu-Gi-Oh! Duel Terminal" Series. It is an ancient dragon, magically infused with the pure essence of absolute zero, who was sealed inside the Ice Barrier to prevent its power from sending the planet into an everlasting ice age.
"Mirror of the Ice Barrier:" The Mirror that originally sealed Trishula
Appearance
Trishula is a dragon with three heads. Its scales are made of blue ice, some of which are white while others are navy. It has two large wings used mainly for keeping balance and pouncing. It also has four clawed limbs: two which serve as its arms and two which serve as legs.
History
Life in the First Ancient World
Through unknown means, Trishula was sealed within a magical mirror during ancient times by several wizards who used cryokinetic magic to survive its harsh power. The wizards who sealed Trishula used its power to create a magical barrier made of ice that would shield the rest of the world from the mirror's icy fallout.
Over time, the wizards came to be known by the name of The Ice Barrier, and they safeguarded Trishula's mirror without any problems. At a later point, two ice dragons named Gungnir and Brionac were sealed inside the Ice Barrier with Trishula's mirror. Though they were not as powerful as Trishula, they were easier to tame and their power was harnessed in case the Ice Barrier ever need them to defend themselves.
That time would eventually come when war broke out between the Ice Barrier and three other clans: The Mist Valley, the Flamvell, and the X-Sabers. Although the Ice Barrier had not needed to release any of their dragons against the other clans, the need soon arose when aliens from the Worm Nebula invaded and indiscriminately started attacking all of the factions simultaneously. The four clans each decided to focus on fighting the Worms instead of each other, though not united. Each clan released some of their mightiest weapons, soldiers, and resources to combat the Worms. The Ice Barrier decided to release Brionac as their means of keeping the Worms from penetrating the Ice Barrier walls.
Due to the Worms invading the Naturia Forest, all of the clans decided to band together and contribute their technologies to create the Ally of Justice machines. When the Ally of Justice started to push the Worms back, the Fabled clan arose amidst all of the chaos and started attacking just as indiscriminately as the Worms. This prompted the Ice Barrier to release Gungnir and have it target the Fabled.
Afraid that any other, more powerful threat may emerge, the Ice Barrier considered trying to use spiritualism to harness Trishula's power for their cause. The Worms then opened a portal directly to the Worm Nebula and the Worm Zero came through, which caused untold devastation. The Ice Barrier's attempts to harness Trishula's power failed, so they instead decided to just break the seal on the Trishula's mirror and let Trishula run rampant on the Worms. However, upon breaking the seal, Trishula turned on them and the dragon managed to blanket the Earth in a deep freeze within hours.
Though the Worms and Fabled were defeated, Trishula singlehandedly killed all life on the planet. Without any proper way to sense what was food and what was not, Trishula starved to death and became a frozen fossil in an ice age that lasted for millions of years.
Legacy in the Second Ancient World
"Evilswarm Ouroboros:" Trishula's infested zombie form
Trishula, Gungnir and Brionac had all remained as fossil statues surrounding the land of the Ice Barrier since the end of the first world. Eventually, an evil mutant virus called the Lswarm virus infested the land and brought them back to life as insect-like zombies. Brionac became Evilswarm Bahamut, Gungnir became Evilswarm Ophion and Trishula became Evilswarm Ouroboros. Each of them slaughtered thousands, and though Bahamut and Ophion were eventually subdued, Ouroboros came to blows with the Constellar Ptolemy M7. After a hard-fought battle, the Ptolemy finally slew Ouroboros, and its decaying essence became Trishula again. The three ice dragons would not be used for their power again, until Shurit the Strategist of the Nekroz channeled their essence for the Nekroz clan. An evil Construct of Gem-Knight Lapis was brought back to life by a further mutated and now sentient Lswarm Virus, now called the Shaddoll Virus.
"Nekroz of Trishula:" Trishula's essence harnessed by Shurit
This Construct would prove to be too hard for anyone to stop, so the Nekroz channeled Trishula and Gungnir into Shurit and his companion Emilia, respectively. They used their new powers to permanently bind the Construct to a machine called the Apoqliphort Towers in an unthawable ice. This would only prove to be a temporary measure, as an evil machine named Devyaty pulled Trishula, Gungnir and Brionac's essences from between the dimensions of life and death, using it to thaw the Construct and shatter the Towers. The powers of the Construct, Devyaty and the three ice dragons were combined in order to form a new creature called Anoyatyllis, who then started attacking every living thing in its path.
"El Shaddoll Anoyatyllis:" Devyaty and the Construct combined with the ice dragons' power
The Nekroz managed to fight back using a legendary spear, which shattered the fusion and Devyaty.
Though it's not explicitly stated, it can be assumed that when Devyaty was destroyed, Trishula's essence was freed and returned to the Duel Monsters Spirit World.
Personality
Though Trishula is powerful, it is still a wild animal and does not have the capacity to tell friend from foe or think things through. Upon being released from its mirror, Trishula mindlessly froze everything, not even accounting for how it would find food or if anything beneficial to its survival would remain intact.
Powers & Abilities
Being made of blue ice, Trishula is much heavier and more durable than most dragons. As Evilswarm Ouroboros, it can be seen holding its own against a machine of the same size in terms of brute strength.
Trishula is said to be the physical embodiment of absolute zero. Its icy power is strong enough to where, even while sealed in a pocket dimension, it is still capable of freezing the world or at least damaging some ecosystems. Upon being released from the Mirror of the Ice Barrier, Trishula devastated all of its enemies and managed to freeze the world over in less than a day. Its power was so cold and thorough that it managed to keep the Earth frozen in time for millions of years.