Iconian gateway: something that can manufacture, control, or weaponize it.We've only seen Iconian portals, and that showed up in DS9 as well, and they wouldn't destroy or save the galaxy directly. Dyson sphere would be cool, but that also has no clear connection to such power. The Chase revealed that many aliens are related, but there was no big tech artefact IIRC.
Which powerful ancient artefact tech would be kept on a Romulan science (not scout) ship? We only saw one in Next Phase![]()
The Chase had a Computer program written into DNA. There could be a more expansive primer out there for more species, which could be used for good or ill.
Dyson builders or their tech could make a really big splash. They would have been able to move a star, replicate robots, and deconstruct a solar system to make it work.