A few decades were perfectly acceptable. The people's lifespans had generally surpassed five hundred years, so a few decades amounted to barely a tenth or a fifth of their lives. They still had a long way to go.
Best of all, having a few decades to ease into it meant they didn't have to worry about a sudden influx of Psionicists disrupting the existing social order and causing widespread unrest.
As he examined the branching Fate Lines, he found that the Empire's fate had shifted somewhat after the Soul Sea came into being. He scrutinized the new Fate Lines one by one, searching for potential dangers.
After a long while, he slowly looked away. "We can roll it out across the Empire once it's been running for a while and we're sure there's no danger."
Of course, putting it into practice wasn't that simple. In an apparent effort to heed public opinion, the government website selected ten billion volunteers for the experiment each month. After twelve consecutive rounds over the course of a year, they finally confirmed that the Soul Sea was harmless and expanded access, raising the number to a trillion people a month.
At that point, the government no longer managed the process centrally. Selected citizens went directly to their local temple for a divine rune-branding ceremony. Local state churches, Order of the Holy Hammer branches, and colonial security forces then jointly oversaw them to prevent possible cases of "demonic possession."
Two years later, the experiment had been running for three years. After confirming that the risks of the Soul Sea were manageable, the government opened the channel even further, ushering in the age of Universal Awakening.
"I never expected there to be a bonus like this." The Emperor on his throne was busy constructing new sanctuary worlds.