Star Essence

is the third of the 5 available essences in the game. It is used for focuscrafting and alchemy. Harnessing star essences can only level the player's Energy Harnessing level up to a maximum of 201 and it costs 25 production points. The crystals have a chance of dropping Essential Mana, Aurora Scarabs and Speed Potions instead of the essence.

Source
Dropped by monsters and crystals from the following provinces:
 * Essenia
 * Essenian Crest
 * Silent Hills
 * Serenity Valley
 * Blessing Basin
 * Blightwood
 * Shakan's Revenge
 * Twisted Vale
 * Timeless Woods


 * Ostgarath
 * Mistmoor Island


 * Poporia
 * Lake of Tears

Best place to farm is probably valley north of Tria.
 * Val Aureum
 * Aurum Road