Undecember Farming Elements via Puru Element Depository

This is most likely the best way to gain many of the elements that are required for upgrading your runes. You need to find the loot goblin and then start to attack it until it falls over. If you get lucky it will spawn a special portal that leaves into one of three different rooms. The one that was offered this time was Puru Element Depository, which drops tons of red, green and blue elements.