Yes, you need to take the other paths in order to place all three artifacts. Each time you will meet Altheides and have to answer two questions. The answer to the first question is always what the artifact stands for (Highlight for spoilers):"Destinae D .= Knowledge, Chaos M. = Chaos, Astral D. = Life".
The second question is always about a person or persons. The only one that is really difficult is the one down the Higardi path where you place the DD. Again, highlight for spoilers:"DD = Higardi/Man, CM = Dark Savant, AD = Phoonzang.
Ascension Peak may be the last area of the game but it's also one of the biggest and there are a lot of tough battles there. You will find yourself fighting different types of creatures down each of the different paths. Good luck completing the game (and I hope you remembered to diffuse the bomb
)!