The Eternity Core (エタニティコア Etaniti Koa) is a high energy object and a legendary device from Ultraman Trigger: New Generation Tiga.
A device capable of reshaping the universe or even creating a second Big Bang, the Eternity Core held an immense amount of power, and was kept deep below the surface of the Earth. 30 million years prior to the series, the Eternity Core's power caused monsters to run wild across the globe. Some of these monsters being Gomora, Deathdrago, Gamakugira and Gubila. The Giants of Darkness previously arrived on Earth to find the object, hoping to use it to reshape the entire universe to their favor, but were defeated by the combined forces of Ultraman Trigger and the Terran Protection Team, causing them to be banished to the edge of the universe in petrified forms.
Ultraman Trigger: New Generation Tiga
In the present day, the Giants of Darkness resume their mission to find the energy source by targeting Yuna Shizuma, hoping to extract the location of the core from Yuzare's spirit within her. Akito speculated that current cases of reappearing monsters are due to the Eternity Core becoming active again.
After Kengo Manaka was sent back in time as a result of being banished from Trigger by Carmeara's Curse of Darkness, he bore witness to, and inadvertently played a role in the events of the past. After the Giants of Darkness forced Yuzare to open the gate to the Eternity Core, he traveled through the portal to the device's chamber, where he saw that Carmeara had selected Trigger Dark as the first of the Giants of Darkness to receive the Eternity Core's power. However, at the last second, he stood before the Eternity Core and used the Ancient Sparklence to bond with Trigger Dark. Eventually, Kengo managed to reach Trigger's heart, and found out that he and Trigger are one and the same. They became one and Trigger Dark turned from the darkness, becoming Ultraman Trigger Multi Type and proceeded to fight against his former comrades. Trigger was losing at first until Yuzare sent the Eternity Core's power to Kengo at the cost of her own life. The light started to petrify Trigger and the Giants of Darkness until Trigger pushed his opponents into space while they turned into stone, with Trigger's own petrified remains landing on Mars and thus completing the time loop that started all these events.
Kengo, now brought to the present, fought against Trigger Dark and the Giants of Darkness. He struggled until Yuzare's spirit comes forth from the ring she left behind and through it, Yuna grants Trigger a fragment of the Eternity Core, allowing him to become Glitter Trigger Eternity. Ultraman Ribut trained him and reminded Kengo that while he was an incarnation of light, he was also just a human.However, he was unable to control its power until
Eventually, Yuzare's power within Yuna fully awakened. Ignis abducted her and brought her to the altar where Yuzare once opened the gate to the Eternity Core and had Yuna do the same, intending to revive his race using the Eternity Core's power. He then confronted Hudram there. Ignis used Trigger Dark's powers and defeated Hudram, and then walked away from the Eternity Core now that he had found new friends on the Earth.
After Darrgon was killed, Carmeara kidnapped Yuna and opened the way to the Eternity Core. Having absorbed the power of darkness from Hudram and Darrgon prior, she touched the Eternity Core and took its energy while polluting it with her own darkness. Her body was torn apart as she transformed into Megalothor.
After Carmeara had transformed, the Eternity Core began to become unstable as a result of the darkness it had absorbed. Witnessing a vision of the Core in its present state, Yuna tried to warn Carmeara of the risk of the Eternity Core erasing the Universe, but Carmeara ignored her pleas, declaring that she didn't care if the Universe was destroyed as long as she had Trigger.
As the Eternity Core's instability increased, it began to expand in size, releasing vast amounts of energy that erupted through the ground and began incinerating areas of Tokyo. If the Eternity Core wasn't contained, it would result in both the Core and the Earth itself exploding, initiating a new Big Bang. During the first fight against Megalothor's second form, Trigger absorbed energy directly from the Core in an attempt to empower Glitter Trigger Eternity's attacks and contain Megalothor's dark powers, but the energies reacted, producing a massive explosion that reverted Trigger back to Kengo, forcing him to escape with Ignis and GUTS-Select.
However, his encounter with the Core made Kengo realise that he needed its power to stop Carmeara, as it was the only thing on Earth that equaled Megalothor's sheer strength, and its combined powers of Light and Darkness would be sufficient to stop her assault on the planet. After Yuna recalled how Kengo had turned Trigger from a Giant of Darkness to a Giant of Light, Ignis formulated a plan to transfer Trigger Dark's remaining Darkness to Trigger, which would give Trigger control over both forces. Kengo deduced that this resultant state was Trigger's true form, and that it would be capable of neutralizing Carmeara's dark energy and take it away from her after being amplified by the Eternity Core. Yuna would be responsible for gathering the energy from the Eternity Core, which would then be fired from the Nursedessei's Nurse Cannon.
After Ignis used his Sparklence to provide Kengo with Trigger Dark's darkness, he was granted a brand new Hyper Key for Trigger; Trigger Truth. With this new form, Trigger could finally control the energy of the Eternity Core in its entirety. Though Kengo was able to destroy Megalothor using Trigger's true form, it still wasn't enough to purify the Eternity Core, and Trigger Dark's essence returned to Ignis. Knowing what he had to do, Kengo departed from GUTS-Select to stabilize the Eternity Core by being contained within it. As he slumbered within the Eternity Core, it began to revert back to its pure state.
Ultraman Trigger: Episode Z
Kengo Manaka had been stabilizing the Eternity Core for two years, and with the ceasing of its fluctuations, the monsters on the Earth had also stopped rampaging. However, the process was draining Kengo of his life, and would kill him if it were allowed to continue. If he disappeared, the Eternity Core would go out of control again, putting the Earth in danger once again. Kengo appeared in one of Yuna's visions, alerting her of the danger he was in.
To displace Kengo from the Core while keeping it intact, GUTS-Select agreed to use the energy of the Sun, fired at the Eternity Core by using the Sol satellite that the TPU had built. The Leyrah cultists attached devices they created to the pillars around the Eternity Core's entrance to change the sunlight's energy into a form of light that can be accepted by the Eternity Core, successfully managing to remove Kengo from it. However, in the process, his GUTS Hyper Keys scattered out and went missing. GUTS-Select threw a party for Kengo to celebrate his return.
As the battle against Evil Trigger raged on, Yuna decided to approach the Eternity Core and splinter a fragment from it like Yuzare did 30 million years ago, despite being aware of the risk. In the process, she sacrificed Yuzare's ring and the gateway tower, but granted Trigger the power to make a comeback, defeating Destrudos, who was summoned by Celebro after Haruki forced him out. Trigger, Trigger Dark and Ultraman Z then finish off Evil Trigger after he had gone mad and grew to giant size.
When the battle was over, Yuna watched as the Eternity Core's gateway tower crumbled, saying goodbye to Yuzare, finally putting an end to the fates that bound them for 30 million years.
The exact nature of the Eternity Core is unknown, saved from being an energy object, but it is said that it has the power equal to an entire universe. It is also powerful enough to reshape the universe to their users' liking, as the Giants of Darkness wanted to turn it to suit their needs.
- Uchusen 173 page 81