Giant rat

From Ardrana

Giant rats are vile beasts that plague underground areas such as crypts and dungeons. Their burrows honeycomb many graveyards, where they cheat ghouls of their prizes by tunneling to newly interred corpses.

Giant rats are brown/black in color with white underbellies, and are related to the brown rat, with fatter bodies and shorter tails. As with normal rats, any creature bitten by a giant rat has a small chance of catching a debilitating disease. Giant rats avoid attacking strong parties unless driven by hunger or commanded by creatures such as vampires and wererats. Giant rats are fearful of fire and flee from it except if driven by hunger or magic. They are excellent swimmers and can attack in water as well as on land.

Note: Giant rats originally appeared in this form in the 2nd Edition Monstrous Manual for the AD&D game from TSR. Their use here is for the purposes of providing context for the campaign only.