After spending hours to get to the boss who is impossible to kill and losing 2 of the 4 people that started, the last 2 of us were running out of cards. I let my partner leave, first, to get mana and change his deck to better work on this boss. He ported back, then I left, for lack of cards and not getting him past 1/2 dead. I refilled, changed my deck, (took 5 mins) and couldn't get back to him. No X to go back to the dungeon and I couldn't port back to my partner. I went through the front, to try to get around to where I was, but couldn't do that either. No, he hadn't killed the boss. What did I do wrong? Never had this happen in any other dungeon.
The Rasputin dungeon has a timer built in. On round 30, the sky anchor falls and instantly kills anyone still in the battle. Since you're describing a long and drawn-out battle, I'd guess this is what happened. The sky anchor might have fallen on your partner while you were away, thus ending the battle.
Alia Misthaven