A transmatter portal is a construct that is capable of instantaneous travel between any two points in the universe. With the usage of breach technology, a transmatter portal can also be used to travel to any other universe in the multiverse.
Roulette began working with Maaldorian slavers to kidnap human subjects. They used a transmatter portal located under a fake health clinic to transport humans from Earth to Slavers' Moon in order to sell them into the galactic slave market. Kara Danvers and Mon-El investigated a string of missing persons and discovered their plot. They both went through the portal to rescue the kidnapped humans. When Alex Danvers led a D.E.O. strikeforce to the portal, J'onn J'onzz recognized that it was a transmatter portal and tasked Agent Winn Schott to get the portal working. He activated it allowing Alex to lead the D.E.O. on a rescue mission to Slavers' Moon. When they returned with the rescued human captives, Winn reactivated the portal allowing everyone back to Earth.
The D.E.O. kept the Maaldorians' portal on Earth and later reconfigured it to transport them onto Lar Gand and Rhea's spaceship. J'onn, Kara, and Winn used it to rescue Mon-El and used it again to transport themselves back down to Earth.
Rhea went to Lena Luthor with a proposal to build their own transmatter portal. Lena thought the portal's possible benefits would greatly help the Earth and Rhea claimed that she wanted to use it to return home. Lena and L-Corp built a giant prototype outside National City but there were having problems stabilizing it. Whenever they turned it on, it caused Phorians in National City to go berserk and unleash their psychic powers out on everything and everyone around them. When Lena managed to stabilize the power, Rhea revealed that the portal was being used to bring all the scattered Daxamite ships across the universe to Earth. Supergirl tried to destroy it but it was self-sufficient and had a barrier to protect it as hundreds of ships came through it into National City.
Battle for Earth
When Alura takes Kara to Zor-El's lab where she finds a transmatter portal. Using the holo-Alura on Earth, Kara sends a message to Winn to help get the D.E.O.'s portal linked to theirs. Before Winn can activate his portal, the dark Kryptonians attack the D.E.O. wanting Purity and Pestilence's blood to restore Reign with. Kara uses the holo-Alura to trick a dark Kryptonian into activating the portal. Kara, Mon-El and Alura rush through to join the fight.
When an antimatter wave was detected moving through Earth-38's universe, it was decided that the best thing to do for the time being was to get as many denizens of Earth-38 to Earth-1 as possible; knowing that Earth-1 would be the last Earth that the antimatter wave would reach. Being fully aware that an interdimensional extrapolator wouldn't be able to fill their need, on J'onn Jonzz's urging, Alex reached out to Lena Luthor, asking her to construct an enormous transmatter portal to transport as many people from Earth-38 to Earth-1 as possible. To pull this off, J'onn contacted every alien refugee he knew, knowing that they'd all come to Earth on some type of ship, and that the ships could be loaded up with residents of their universe to transport them all to Earth-1 more quickly. Ultimately, of the 7.53 billion citizens of Earth-38, three billion made it to Earth-1, with one billion making it to safety due to Oliver's refusal to give up, even when the Monitor told him the battle was lost and that they needed to retreat, though this ultimately resulted in Oliver being killed fighting to buy more time to evacuate the Earth's residents.
Behind the scenes
- In DC Comics, the Transmatter Portal is a device utilized in the 31st century by a great many species throughout the universe, as well as the coalition of the United Planets.