Shadow Vermin

These are the enemies encountered in Hyrule Castle sewers, after first being transformed into Wolf Link and escaping with Midna.

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 you swim across the water, and can sometimes be hard to spot until they get very close.

Shadow Vermin's also make an appearance within the Palace of Twilight.

Not to be confused with the Ghoul Rats found elsewhere.