Best Blowout Support Event 2017 until July 04 (Europe) or Aug 23 (USA).  

Revelations (v6.7) patch introduced alchemy in Viron, which can transmute "useless" items into potentially valuable items like Dragon Heart and Symbol of Naraka. See [v6.7 Feature] Alchemy for a list of possible drops, and Alchemical Materials for a list of ingredients available in v6.7.

The following test was done with three Grade 3 alchemical ingredients, then upgraded by adding more vis. The total rank is thus 10 (3+3+3+1), costing 198,000 vis. This was done 116 times at a total cost of 22,968,000 vis. The results are as follows: 

I got 1 Symbol of Naraka out of 116 refinements. The most common drop was 10 Hermes Potions (25/116), followed by 3 HQ Gems (20/116) and 3 Rough Stones (19/116).