Flare is a hunter ability learned at level 38. It reveals any stealthed units within 10 yards for 20 seconds. It costs 1 35 to learn from a trainer.
Notes
If you have a suspicion there's a hidden or invisible unit in an area, you can Flare to reveal any of them. This can be especially useful in PvP or in places where you know there are stealthed mobs, such as the western wing of Dire Maul.
Using Flare now leaves a bright light on the ground, possibly alerting stealthed units you are nearby.
There is a brief period of time after using the spell that a rogue, if properly positioned, can sneak in before the flare effect begins and get an opener off.
Patch changes
Patch 2.4.0 (25-Mar-2008): Casting Flare while in any way not visible, will no longer cause your flare to be invisible to other players.
Patch 2.1.0 (22-May-2007): Flare cooldown increased to 20 seconds, and duration reduced to 20 seconds.
Patch 2.0.3 (09-Jan-2007): The hunter spell "Flare" will now properly reveal Mages that used "Invisibility".
Patch 1.7.0 (13-Sep-2005): Fixed the tooltip to accurately reflect the actual radius of the effect.