Complete Storyline #65: "Mysterious Box".
To trigger this storyline requires you to meet 4 criteria:
1. To have completed Storyline #51: "Tome of Knowledge" to unlock the Mind element
2. To have retired at least once since completing step 1.
3. Reach level 35 in your Primary Element
4. Have exactly 123 Mind Shards in your inventory
When you meet all of these criteria at the same time the Storyline will trigger and you will be asked to put 30 Silk into a box. Once you have done this you will be asked to put another 30 Silk into the box. Lastly, You will then create a tracking stone which needs Earth level 30, Mind level 30, 500k Earth Essence and 7,500 Mana. After which you will need to put a final 30 silk into the box and the storyline will complete and the achievement will pop.