This achievement is gained upon defeating the following rare monsters in The Plane of Mischief:

an asinine ape
an astray hand
a barmy burglar
a bogus treasure chest
a bouncing bunny
Bzzibuzzana
a craven rascal
a forsaken hand
a fraudulent chest
a frolicking performer
a funky skunk
a gifted sphinx
a gorilla prodigy
a gorilla professor
the Grand Gardener
a hedge magus
a hedge soldier
an irritating mushroom
a maddened mushroom man
the Master of Mayhem
a method actor
an obsessed patron
a paradoxical sphinx
a savvy sphinx
a theatre fanatic
a troublesome charlatan
a wicked performer
a witty sphinx

Hidden Steps

• Plane of Mischief - Availability