Arcane Vortex
An Arcane Vortex appears to be a rip in the dimensional fabric, a sort of wormhole where the Twisting Nether's very essence appears because of the magical tears in the broken world of Draenor.
An engineer can use a 
[Zapthrottle Mote Extractor] on these clouds to collect varying amounts of 
[Mote of Mana].
Visibility
Under normal circumstances Arcane Vortices are invisible; they can only be noticed by their mana-regenerating effect: An Arcane Vortex regenerates 20 Mana per second on any mob or character within a 40-yard radius. Golden sparkling on all creatures in an area is a sure sign of a nearby vortex.
Engineers can have [Zapthrottle Mote Extractor] in their inventory in order to see Arcane Vortices. Alternatively, warlocks can use their 
[Detect Invisibility] ability.
Locations
As Arcane Vortices wander, it is difficult to give exact locations. You can notice their presence by the golden sparkling on all nearby creatures, even if you do not have goggles equipped.
Some locations where Arcane Vortices have been found in the past:
- south-west of Manaforge B'naar
- east of Area 52 between the giants
- next to the gryphon master of Area 52
- in Kirin'Var Village, north of The Violet Tower (this one used to be below ground)
Patch changes
Patch 2.0.3 (2007-01-09): Added.