Shadow Vermin

From Zelda Wiki.org

Shadow Vermin
Game(s)	Twilight Princess
Habitat(s)	Hyrule Castle Sewers Palace of Twilight
Effective Weapons	Wolf Link

Shadow Vermin are enemies encountered in Hyrule Castle sewers after first being transformed into Wolf Link and escaping with Midna. These are not to be confused with the Ghoul Rats found elsewhere.

They appear as small, black squid-like creatures which attack by flailing randomly at Link. Fighting them can be tricky, as they will attack while swimming across the water, and can sometimes be hard to spot until they get very close. They are quite fast, and can attack when least expected.

Shadow Vermin also make an appearance within the Palace of Twilight. The only difference is there is no water for them to skim across.