This illusion is from the Gnoll Disguise created during the quest, "Gihbra #4: The Arms of Brell" (Underfoot exp. - Volska's Husk zone).
It appears to only work in Volska's Husk zone. If clicked elsewhere you just see a yellow text message:
"There is no need to use the disguise here."
*sigh* Thanks for taking some of the fun out of your world, SOE. :(