You get this quest by speaking to Whysper who is found on the southwest platform in Qintarra. She is near the NPC, Fawn. She will tell you that she is a scientist (a very un-elf-like profession) and that she is cataloging will-o-wisps. She will ask you to find the rare Vol'ars Wisp Essence but will only say the wisps are rare and can be found somewhere in the Glimmering Forest. When you get the essence return to Qintarra and give it to Whysper. She will reward you with a Scroll of Succour Beast.
There are a couple of ways to find this essence:
1. Go to The Old Lagoon which is a distant north by northwest of Caladon and right on the western coast. It is likely that you won't have a map location for this lagoon when you accept this quest. The lagoon's coordinates are 1695 W by 1320 S. You should find numerous "blue" Volar's Wisps floating about the small lagoon there. If you do not, try sleeping a few times until they spawn but make sure you check all around the lagoon, first. They are probably there somewhere. Be aware of the level 25 Slime Demons, Death Lanterns and Will-o-Wisps that are also there. You might also see a non-hostile level 30 Bear Ancient. There is an easily seen arcane chest in the lagoon but it can be somewhat difficult to walk to. It holds only a Kathorn Crystal, Healing Potion, Ruby and a little coin.
2. Use the game's Walking Waypoint Map tool and place lots of waypoints around Qintarra and throughout the Glimmering Forest. Press the Action Button to the right of the map and wander about to trigger random encounters. You may stumble upon a Volar's Wisp. This method can take hours and I do not recommend using it. It is also possible that it may not work. Some patient people may want to use this method to collect some loot for cash and possibly gain a level or two.
Note: You may have seen that some have suggested to use the wisp essence in the treasure chest at H.T. Parnell's in Tarant. This essence is for a thieves underground quest and it is also NOT a Volar's Wisp Essence, rather, it is a "Will-o-the-Wisp Essence."
Note: In the game Volar's is spelled two ways: Vol'ars (journal and dialogue) and Volar's (inventory essence and the actual wisp).