FusionDex

Koffbat produce a virulent gas that clings to their wings wherever they fly. It only takes a few specks of this gas to produce a coughing fit, which is enough of a distraction for them to strike their prey.

Over the course of evolution, its hind legs turned into wings. Getting up close to a Koffbat will give you a chance to observe, through its thin skin, the toxic gases swirling inside.