Sun Essence

is the first of the 5 available essences in the game. It is used for focuscrafting and alchemy. Harnessing sun essences can only level the player's Energy Harnessing level up to a maximum of 101. The crystals have a chance of dropping Essential Mana instead of the essence.

Source
Dropped by monsters and crystals from the following provinces:
 * Arcadia
 * Fey Forest
 * Valley of Titans(more specificly at Mags Kulkar on top of hill where Gutrends are)