Middle-earth: Shadow of Mordor - Game of the Year Edition

This is a story-based achievement which can be obtained by completing a story arc in the main game. Please note that the below explanation may contain some very minor spoilers.

You meet Torvin the dwarf during the first main mission along The Sea of Nurn (2nd area of the game). This in turn will unlock his main missions for you to complete. They appear as yellow claw marks on the map.

Torvin has 3 main missions you must complete to earn this achievement.

1. Big Game
2. Hunting Partners
3. The Great White Graug

Mission 3 requires you to down a very powerful Graug enemy. Once you have completed this mission, you will gain the achievement.

Note that with most of Torvin's missions, it is useful to be trying to complete the hunter challenges for that achievement, as "rare" monsters are forced to spawn during Torvin's missions.