XHT-S7 is the multiverse designation of the universe from which Kent "Icon" Powers , MidKnight II, The Runner, and Karen Powers (along with the alternate-future Galatea Future) all call their birth-home.
XHT-S7 is an otherwise average universe that would otherwise have a normal development if not for the accidental incursion of material from another universe that rained down on the planet Earth on October 30, 1938. The material, debris from the death of another universe, arrived in the form of a huge meteor shower, and the extra-dimensional radiation gave certain inhabitants of that planet extra-normal abilities.
In the "Common Multiverse Time" of April, 2007, the multiverse threat known as Alor used his devices to open a giant portal over the Earth. Earth's remaining heroes arrived to try to deal with the event, but discovered much to their horror that this was more powerful than they could ever begin to handle, yet they felt they needed to try anyway. Following MidKnight's lead, Photonis created a hard-light track for The Runner to run around in an attempt to generate enough gravitational pull to force the portal in on itself.
Unfortunately, they had no idea that the portal was Alor's instrument to find and destroy that universe's key "Fixed Point", namely the existence of Photonis. Alor destroyed Photonis, thus forcing that universe to rip apart in entropy. However, at the same time, Kent Powers, along with the help of a cosmic female named "Redemption", attacked Alor and his equipment, forcing a temporary link between XHT-S7 and another universe, sending the surviving heroes near the portal (along with a newly-exiled Galen) to that other universe. Along with Kent Powers, they would be the only survivors of their home universe.
The history of Universe XHT-S7 was revealed in several issues of "Guardians of the Dawn Spotlight" and "The Guardian Powers". It played a key role in both "The Guardian Exiles" and "Time and Changes" storylines.