12 or 13 Minutes Total time, repeatable on failure 10-15? mins, 3? hours on success, ease of quest easy if you don't mess up the kill/harvest aspect and can remember your current number, seems random the order each run. If your dps is low, you may have trouble killing the one up elemental(s) in time.
Click chest at ( -92, 574, -718 ) /waypoint -92, 574, -718 to pick/start quest.
One of the 8 nearby pillars will light up with a glowing ball (looks like a giant version of fury spell lightning ball), only one will be lit up at the picking phase, click it. It ports you down to the rings around the font, you will fight an elemental, when it is dead, use the click item in your quest journal to harvest its mana. (NOTE) This quest seems buggy, if you have a pet or use dots you will kill the killed npc and you will not be able to harvest the mana, use DD spells/CA only and turn off auto attack when using the bauble on the slain creature, failure to do so will in essence force you to fight a new one because it depops/dies properly after 5-8 seconds anyway.
On successful harvest of mana from the elemental, you will be ported back to the pillars, hope you memorized your pillar number, click the correct pillar and charge it, click on wrong pillar and you fail.
Repeat above steps till all 8 pillars are charged correctly.