I completed the ascension process on single player. I used cheats to keep from dying. Dieter is correct, you must first kill all three bosses on the Island. Then you go to the ascension cave at the volcano. The first part of the cave is extremely hot, around 130F. It is all so packed with extremely high level rexs, allos, and gigas. After that you get to the tek cave where you face a final boss. It's really cool, I for sure recommend it, however, doing it yourself without cheating would take an insane amount of time. And if you did take the time to tame all those dinos and you failed, they all die and you start over. I cheated in an extremely high level giga (higher than would normally be able to spawn) and with an ascendant saddle it still died. You don't need to be on official, any server or single player will work fine. With out a tribe, its my opinion, that you would need to cheat to survive.
