Headbang at the exam center
Warning! Potential danger for Hardcore Ironman!
1. Go to ::shops at home, trade the clue items shop and buy a mystic fire staff, a diamond bracelet and rune boots. You need 40 attack and 40 magic to equip the mystic fire staff, and you need 40 defence to equip rune boots.
2. Go to the digsite southwest of varrock by the City teleports > varrock or use a digsite pendant (enchanted ruby necklace), if you have one, go to step 4.
3. Walk east and leave Varrock through the city gates, walk south until you can go no further, walk east through the wooden gates, walk around the high bushes and enter the exam centre. Go to step 5.
4. Rub the digsite pendant, walk south and enter the exam centre.
5. Equip above items and perform the 'headbang' emote, a level 108 double agent will spawn, kill it to finish the clue!