King of the Mountain

Well since no one has posted anything helpful on this achieve, I guess I will be the first. This achieve doesnt even happen until about 10-20 quests AFTER the Fading into Twilight achieve. You literally have to have done every other single quest in the zone before you get this quest.

After completing the quests around the twilight gate you will end up at Initiate Goldmine at the Elementium Depths who will take you on a ride into the depths of the mine. Then you can pick up the quests `Little on the side and While you where here`. In the mine you will get the quest `Rune Ruination` from a rune with is very easy to find. This quest leads to the quest `a fiery Reunion` (kill magmatooth). Almost there..Kill Magmatooth and use the portal to get the quest `Matthias needs you` then `the hammer of twilight` and finally Skullcrusher the mountain.

I had done Fading into Twilight ealier, but now wanted this achievement. After reading comments from WoWhead and flying around Twilight Highlands trying to find quests that I was missing, I end up downloading Quest Completist-addon from curse. Found my quests and got my achievement.