Burning Crystal
From WoWWiki
A Burning Crystal is a "green floating object" in Sunstrider Isle, west of the Sunspire in Eversong Woods, used to power the blood elves' experimentations.[1] Prior to the invasion of the Scourge, the crystals were protected by 
Mana Wyrms. However, the elves' have since lost control over the crystals; the crystals, now unchecked are negatively influencing the Isles wildlife population.
