This section blatantly gives away the mysteries and/or endings of the storylines 4U City Red.
If you haven't read some of those stories, then dude, before you go any further, go read them! This stuff will still be here when you're done.
You have been warned...
Before the rise of 4U City, the native Riff of the Dimension of Rain was betrayed by the same dimensions Dr. Schlock. He used his emergency DFA to teleport into a random wasteland dimension, where Zoë (DoR) died of her wounds.
Living with a carib, Riff worked intensively on modifying DFA technology and monitor dimensions for 30 years before discovering a way back to the Dimension of Rain. He also found a way of looking back in time through the dimensional window, tracing the rise and evolution of 4U city.
DoR Riff is about 72 years older than Sluggy Prime Riff, which explains the beard and his generally old-ish behavior. The current events in the tower happen 80 years after his betrayal, but people from that time haven't died of age yet, due to the effect of medical nanites 2.0 and 3.0, where the first slow aging and the second reset a persons physical age to a stored snapshot. This also erases all memories obtained after the snapshot.
During the 4U City Red story, Riff blows up the 4U City's robotic facility in the city's revolution and navigates through its pipes with Executive Rammer, as he correctly suspects that "His Masterness" lives there. They find the DoR Riff residing inside the 4U City control facility, who reveals the city's story to them both, and installs Rammer as the new "His Masterness" after scolding the Sluggy Prime Riff for destroying his connections with the DFA's satellites, which he was using to fix the Timeless Space of the Dimension of Rain.
When the Sluggy Prime Riff tries to reconnect the satellites, however, two terrible things happen: The 4U City's A.I. comes to regard the whole (and few) human race to be a theat that must be eliminated, and worse, a large army of mutant Outsiders has just come back to the dimension. Fortunately, Riff manipunates the satellites into zapping all the mutants out of the dimension without exteminating what's left of humanity, but just when the DoR Riff is about to congratulate his dimensional counterpart, Riff brings Izzy with him in spite of his promise not to. DoR Riff has an emotional reunion with his wife but becomes angry with his counterpart's betrayal, and when he demands explanations from his Sluggy Prime equivalent, Riff retorts that Izzy is a most skilled hacker who could help them restore the Timeless Space, and adds that, while his intentions are good, DoR Riff cannot mantain 4U City's tyrannical statous quo, and they both should learn from their mistakes rather than simply lament or blame themselves over it.
DoR Riff lost his trust in the original Riff but agree with his views and decides to completely change 4U City's administration. He and Rammer change the control facility from underground to the main tower, creating the city's council that roughly administers the city. The citizens don't control how the council is governs, but they are all free to express their feelings without punisment, and the outsiders are allowed to enter the city if they prove to be harmless, or at least peaceful.
As a punishment for breaking his promise, the Sluggy Prime Riff is forbidden from having any function in the city's council aside from serving coffee, a job that he's forced to do even on holidays, though he doesn't care 'cause at last the 4U City no longer is a dark and drugged dystopia. After about an year, DoR Riff finds both the Sluggy Prime Dimension and it's Zoë version who was badly burned alive by Oasis. It's turned out that the nanites successfuly restored her body but where unable to restore her mind since they didn't know anything about her prevous life. On the day Riff returns to his home dimension, DoR Riff decides to return him about two years after his disappearance in order to prevent Sluggy Prime from having the same fate of the DoR. Riff has other plans, however, he drugs the whole council and vows to avoid the whole incident by returning to the night before Oasis' attack. DoR Riff convinces him that it's a waste of time and brings him back, but it turns out to be a trick, when Riff secretly brings a few nanites with him to analyse Zoe's head in the past, thus successfully becoming able to restore her personality and memories from before Oasis' attack and forcing DoR Riff to return her with Riff. Though angered by the trickery, DoR Riff also praises his counterparts cunning and cleverness before returning to his dimension.