You can not just start this quest by pressing a button rather you have to meet a person Ulman he is the one who can start the quest for you and you can meet him in the East of Sumeru City near the small lake.
After meeting Ulman you have to equip the event Seelie gadget and after that, you have to go to the event location that is near Chatrakam Cave. As you reach the location you will then be able to see a round icon on your mini-map and you have to reach the place.
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As you reach the place you will find blue glowing energy over there and there you have to collect three of the blue energies and that will reveal the treasure.
The Seelie will mark the energy location once you are near to it and each of the energy are located near one and another and after you have collected the three energies a shovel will appear on your mini map.
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You can also see the marked place as it has a beacon and then you need to clear the challage in order to obtain the treasure so after defeating the enemies collect the blue energies dropped by the enemies and you challenge is completed.
And then you will find a ray of light from the ground and there you will have to dig in order to find and claim the treasure and you get 10 primogems and some ancient iron coins as reward.
And you can easily exchange it for primogems and Mini Seelie in the shop and you are now done with your quest.
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