Eriksen was discharged from a local hospital on Friday and visited his teammates at training that day as they prepared for Monday's pivotal clash.
Needing a victory to have any chance of progression, Mikkel Damsgaard lit the touchpaper with a 38th-minute wonder goal on a head-spinning night.
It was only half the story though as Denmark's fate was never in their own hands and they were still indebted to Belgium who beat Finland 2-0 in St. Petersburg.
Having lost their opening two games in the wake of Eriksen's cardiac arrest, Denmark went through as runners-up and will face Wales next.
Belgium finished top of Group B with a maximum nine points with Denmark, Finland and Russia all on three points but with the Danes ahead on goal difference.
"It's so insane that we've gone through. This team, these players. It's great to be a part of it," said Damsgaard, the 20-year-old who has stepped into the stricken Eriksen's boots.
"I have never dreamed of being a part of something so big, so it's a great feeling."
"If anyone deserves this, it's our players,'' Denmark coach Kasper Hjulmand said. "I can't imagine how they managed to come back from what they went through. So big credit to the boys.'
"It is hard to describe what this team has been through the past few weeks, but we are thinking about Christian all the way. The team spirit and how everyone contributed is amazing.
"We played three games on a very high level and our players deserve this."
Other than a Pierre-Emile Hojbjerg shot that fizzed wide early on, Denmark were struggling to make much headway against a disciplined Russia side for whom Alexander Golovin could have opened the scoring after a weaving run.
With no margin for error, there was a tension about Denmark's play and Russia had briefly turned down the noise being generated by the 23,000-strong crowd resembling a solid red wall.
"It's the first time I've seen support like this," Russia keeper Matvei Safonov said. "One of their players just completes a pass and the whole stadium is on their feet."
But that all changed with a moment of magic from Damsgaard, Eriksen's replacement, in the 38th minute.
Receiving a pass from Hojbjerg, he took a silky touch with his left foot and opened his body to swerve a majestic shot beyond Russia keeper Matvei Safonov.
If Denmark's opener was sublime, then their second on the hour mark was ridiculous. Zobnin inexplicably played a pass back towards his keeper without looking and Poulsen completed the simplest of tasks to score.
Denmark were rampant but in the space of seconds everything went flat as Russia were awarded a penalty after Jannik Vestergaard fouled Alexander Sobolev -- and giant striker Dzyuba thumped the ball past Kasper Schmeichel to revive Russian hopes.
As news drifted through that Belgium had taken the lead against Finland, the mood turned to jubilation as Christensen and Maehle completed a sensational evening.
"The second goal basically came out of nowhere and it did not give us much cause for optimism,'' Russia coach Stanislav Cherchesov said. "Then we allowed two counterattacks and we paid for those with two goals.''
After the final whistle, the whole Danish team formed a circle at the center of the field to follow the last minutes of the Belgium game before doing a lap of honor in front of their serenading supporters.
"It's a relief," Maehle said, "and a redemption.''