Atlant progressed to the semifinals of the Gagarin Cup, edging in front of favorites SKA St. Petersburg in the seventh game of their series.
The Moscow region side collected a 3-2 overtime win in St. Pete and won the best-of-seven series with a 4-3 scoreline.
In regular time, Maksim Rybin twice gave SKA the lead against Atlant, but the visitors managed to equalize on both occasions.
The Moscow region side made it 2-2 with five minutes remaining in the third period, with the goal being a blunder for home netminder Jakub Stepanek.
The Czech keeper tried to start another SKA attack, but hit Aleksandr Nesterov and could only watch as the puck ricocheted into his unprotected goal.
The fate of the series was to be decided in overtime, in which home player Aleksey Semenov got a two-minute penalty for hooking 68 minutes and 32 seconds into the game.
Twenty seconds later, Atlant converted the powerplay, with Dmitry Bykov becoming the hero for the guests, who entered the series as underdogs.
The Moscow region side progressed to the Eastern Conference finals to face Lokomotiv Yaroslavl for a chance to take home the Gagarin Cup.