Used to Synergize Astral Matter for the quest called "The Wondrous Whatchamacallit" which rewards the user with a Portafurnace.
The blonde hume with glasses wearing a white crafting apron and red mits, Selliste in Bastok Mines at (K-7) provides the The Wondrous Whatchamacallit quest and reward. The quest is not repeatable.
Portafurnace (Rare) (Exclusive)
[Neck]
Lv.1 All Jobs
The Portafurnace is a pendant fashioned to resemble a miniature synergy furnace, this handy device allows the wearer to summon the full-sized apparatus from almost any location.
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Portafurnace has a 15 second cool down, 1 minute to reuse, Level 1, All Jobs. and Unlimited Charges.
Tidestones (Rare) are found at the ??? that is located next to the Water Protocrystal in Cloister of Tides zone.
A quick way to get here is to have level 20 or higher Summoner and follow the quest Trial Size Trial by Water and obtain the Mini Tuning Fork of Water to warp there instantly. Please note that if you completed this quest in the past, you cannot retake this shortcut.