FusionDex

Onfing release sulfuric gas from the vents in their bodies to ward off predators. To maintain this defense mechanism, they must constantly consume sulfur, forcing them to live in areas with high sulfur content.

Getting up close to a Onfing will give you a chance to observe, through its thin skin, the toxic gases swirling inside. There is a magnet in its brain that prevents an Onfing from losing direction while tunneling.