New Prysmos

Existing deep in Cybertron's underground, New Prysmos is a fragment of the lost world of Prysmos recreated through the power of the Talisman. Little more than a scrap of city compared to the grand metropolises of their lost homeworld, its cramped conditions have led some of the Prysmosians who inhabit it to compare it to a refugee camp.
Fiction
IDW Generation 1 continuity
Prysmos was once a world where magic ruled before advances in technology made the arcana vast all but redundant. The technophobic sorcerer Merklynn orchestrated the rebirth of magic across his planet but accidentally prompted the destruction of the world as its three suns moved out of alignment. Hoping to find a new world to colonize, Merklynn found his way to Earth shortly before World War II, where he disguised himself as "Garrison Kreiger". First Strike #6
When Joe Colton came to Kreiger for aid in ending the Cybertronian threat to Earth through usage of the mysterious Talisman, First Strike #0 Kreiger saw the chance to use the Talisman to terraform Cybertron into a reborn copy of Prysmos.
The resistance he faced prompted him to activate the Talisman prematurely, only managing to transform a small portion of the planet into "New Prysmos" which he claimed would be the staging ground to wipe away all technology from the galaxy and bring about a new "Age of Magic".
Reflecting on the situation, Scarlett observed that New Prysmos' creation had caused a substantial energon drain which, ironically, made the Cybertronians need their alliance with Earth, and the victory was bittersweet as a result. Cybertronian Security Forces investigated the energy field around New Prysmos, but were unable to penetrate it. First Strike #6 A small amount of Prysmosian refugees came to inhabit the city over the following weeks. Schismatic
After attending Sideswipe's funeral, Kup went off to investigate the underground city. The Dead Come Home, Part 1 In her opening speech at the electoral debates, Windblade pledged to protect the people from "the creatures" living underground. The Chosen One
The Cybertronians eventually arrested Merklynn as a war criminal and erected a quarantine shield around New Prysmos to prevent its energies from spreading outward. Weeks later, Windblade sent Kup and Ironhide to negotiate with the Prymosians while Wheeljack and Breakdown were sent to examine the Talisman. After Talisman energy had disintegrated Breakdown's arm however, Wheeljack discovered the quarantine shield was ineffective and Talisman energy was continuing to spread outwards from the city. Schismatic
Trivia
- The nature of the shield around New Prysmos is contradictory. While First Strike makes it clear that it was set up by Merklynn to keep Cybertronians out, Transformers vs. Visionaries describes it as a Cybertronian creation to keep Prysmosians in. It's also not entirely clear how the Prysmosians got in there in the first place.

