Ghoul Rat

Ghoul Rats are found in dark environments such as the Arbiter's Grounds and Hyrule Castle in Twilight Princess. These invisible creatures will not hurt Link directly, but will cling to him and slow him down significantly leaving him vulnerable to other enemies. Link will also be unable to jump off ledges at full speed with Ghoul Rats clinging to him, and will sink much more quickly in quicksand.

Ghoul Rats can be detected by transforming into wolf form and using Link's heightened senses. One can also tell if there are ghost rodents attached, if Link starts walking like he's wearing the Iron Boots, or if Midna starts freaking out. Also, look for puffs of dust originating from nowhere or disembodied squeaking. The observant can use these to get the jump on Ghoul Rats. Only by using Wolf Link's senses is it possible to defeat Ghoul Rats. A single Spin Attack will destroy any rats clinging to Link in wolf form.