This achievement is still very unclear/misleading. Doing this just now on my second run through of SotO story, I used a T3 motivation at the point where it asks me to scan for a higher level rift...which technically I was doing since I had a T3 motivation active. Completed the rift, consumed the motivation...no achieve. Only by reading this thread after was I able to discern that you have to use the quest-provided T2 motivation to push the quest to "Complete a tier 1, 2 or 3 hunt in Amnytas", THEN use a T3 motivation (or look around/wait for another person doing so), then complete that rift to get credit.