I got to level 9 before trying to get this achievement. First fast travel to the town of Bolmus Populi and head right over the mountain. On the Right face of a mountain is a huge rock monster (Magna). Speak to him and he will take you to The Cliffs of Erin. From here go as far left as you can and then as far up as you can and you will see Tristis sitting at the edge of a cliff. Speak to Tristis and the achievement is yours.