Firstly, before you can start this quest chain you must have completed Episode 4.
In Korinthia you will find mysterious woman outside the Temple of Aphrodite, this is where you accept the quest "Test of Judgement". Complete the quest, return to the woman and depending on your choice you will then get either "Test of Faith" or "Test of Character" quests. Complete your respective quest, return to the woman and you will now receive "Test of Adaptability" quest. Once again, complete the quest, return to the woman to finally receive "Test of Courage" quest. Complete the quest and return back to the mysterious woman one last time.
You will now have completed the Divine Intervention quest chain, and unlocked it's respective achievement.