Shadowy Disguise
From Pet Battle Challenge: Blackrock Depths. The duration is ridiculously low imo. It needs to be at least a minute, probably 5 minutes.
The 
Shadowy Disguise is a toy rewarded for completing the Blackrock Depths pet battle dungeon on Challenge Mode, turning your character completely pitch black for 15 seconds with a 5-minute cooldown.
Guide awaiting review
Complete BRD Challenge Mode
Enter the Blackrock Depths pet battle dungeon and clear it on Challenge Mode to earn Shadowy Disguise as a reward.
Use the Toy
Activate Shadowy Disguise to turn your character model, weapons, and accessories completely pitch black for 15 seconds; the toy is off the global cooldown, so you can macro /use Shadowy Disguise into an ability to automatically trigger the effect every 5 minutes.
Tips
Since Shadowy Disguise is off the GCD, you can pair it in a macro with another ability, including the Prismatic Bauble, to trigger both effects simultaneously.
